Data processing apparatus, system and method for if, then, else operation using write priority

• US 6,026,484 A
• Filed: 11/30/1993
• Issued: 02/15/2000
• Est. Priority Date: 11/30/1993
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Golston, Jeremiah E.
• Primary Examiner(s): VU, VIET DUY
• Application Number:
  US08/160,300
• Time in Patent Office: 2,268 Days
• Field of Search: 712/234, 712/220, 712/236, 712/221, 712/225, 712/223, 712/226, 712/227, 710/244, 708/525
• US Class Current: 712/226
• CPC Class Codes: G06F 9/30 Arrangements for executing machine instructions, e.g. instruction decode for executing microinstructions G06F9/22
• CPC Class Codes: G06F 9/30058 Conditional branch instructions
• CPC Class Codes: G06F 9/30072 to perform conditional operations, e.g. using predicates or guards
• CPC Class Codes: G06F 9/30094 Condition code generation, e.g. Carry, Zero flag

Abstract

A data processing apparatus employs write priority to permit a data processing apparatus to execute an if, then, else operation in a single instruction cycle. The data processing apparatus includes pipelined data unit (110) and address unit (120) operations. The address unit (120) data move operation has a higher write priority than the storing of the data unit (110) operation. The data unit (110) includes an arithmetic logic unit (230) that performs an unconditional operation with the result to be stored in a destination register (200). The address unit (120) sets the address for a data move operation to the same destination register (200). The data move operation is conditional upon the if condition set by the instruction and based upon a set of status bits in a status register (210). The status register (210) includes a plurality of status bits set corresponding to a prior arithmetic logic unit (230) result. The status bits preferably include a negative status bit, a carry status bit, an overflow status bit and a zero status bit. This address unit (120) data move operation, having a higher write priority than the data unit (110) operation, controls the data written into the destination register (200). If the status bits do not match the condition specified in the instruction, then the conditional data move does not take place and the results of the data unit operation are stored in the destination register (200).

Claims

1. A method of conditional data processing operation comprising the steps of:

setting a condition to either a first state or a second state;

performing a first arithmetic/logical operation and storing a first result in a first data register with a first write priority; and

conditionally moving predetermined data into said first data register if said condition has said first state with a second write priority, said second write priority of said conditional move being higher than said first write priority of said first arithmetic/logical operation whereby said first data register stores said predetermined data if said condition has said first state or said first result of said first arithmetic/logical operation if said condition does not have said first state.

2. The method of claim 1, wherein:

said step of setting a condition in either a first state or a second state includes

performing a second arithmetic/logical operation and storing a second result in a second data register with said first write priority,

setting at least one status bit dependent upon said second result, and

storing said at least one status bit in a status register.

3. The method of claim 2, wherein:

said step of setting a condition in either a first state or a second state further includes

moving data stored in said second data register into said second data register with said second write priority, said move thereby having a higher write priority than said storing of said second result whereby said second data register stores unchanged data.

4. The method of claim 2, wherein:

said step of setting a condition in either a first state or a second state wherein

said at least one status bit includes a negative status bit set to said first state if said second result is negative and set to said second state if said second result is not negative.

5. The method of claim 2, wherein:

said step of setting a condition in either a first state or a second state wherein

said at least one status bit includes a carry out status bit set to said first state if said second result generates a carry out and set to said second state if said second result does not generate a carry out.

6. The method of claim 2, wherein:

said step of setting a condition in either a first state or a second state wherein

said at least one status bit includes an overflow status bit set to said first state if said second result generates an overflow and set to said second state if said second result does not generate an overflow.

7. The method of claim 2, wherein:

said step of setting a condition in either a first state or a second state wherein

said at least one status bit includes a zero status bit set to said first state if said second result is zero and set to said second state if said second result is not zero.

8. The method of claim 2, wherein:

said step of setting a condition in either a first state or a second state further includes

setting a plurality of status bits dependent upon said second result, and

storing said plurality of status bits in said status register; and

said step of conditionally moving predetermined data into said first data register if said condition has said first state includes testing a selected set of said plurality of said status bit and conditionally moving said predetermined data into said first register only if each status bit in said selected set of said plurality of status bits has a predetermined state.

9. The method of claim 1, wherein:

said step of conditionally moving predetermined data into said first data register moves said predetermined data from a predetermined memory location to said first data register.

10. The method of claim 1, wherein:

said step of conditionally moving predetermined data into said first data register moves said predetermined data from a third data register to said first data register.

11. A data processing apparatus comprising:

a plurality of data registers;

a status register storing at least one status bit;

an arithmetic logic unit having first and second inputs and an output coupled to said plurality of data registers, said arithmetic logic unit performing an arithmetic or logical operation upon data received at said first and second inputs and generating a result at said output; and

an instruction logic circuit connected to said plurality of data registers, said status register and said arithmetic logic unit, said instruction logic circuit controlling said plurality of data registers, said status register and said arithmetic logic unit in response to a received instruction, said instruction logic circuit in response to a first instruction

controlling said arithmetic logic unit to form a first combination of inputs from first designated source data registers and store a first result in a first designated destination data register with a first write priority, and

controlling said plurality of data registers to conditionally move predetermined data into said first designated destination data register if said at least one status bit in said status register has a predetermined state with a second write priority, said second write priority of said conditional move being higher than said first write priority of said first combination of inputs of said arithmetic logic unit whereby said first designated destination data register stores said predetermined data if said at least one status register has said predetermined state or said result of said first combination if said at least one status register does not have said predetermined state.

12. The data processing apparatus of claim 11, wherein:

said instruction decode logic in response to a second instruction

controlling said arithmetic logic unit to form a second combination of inputs from designated source data registers and store a second result in a second designated destination data register with said first write priority, and

setting said at least one status bit in said status register corresponding to said second result.

13. The data processing apparatus of claim 12, wherein:

said instruction decode logic in response to a second instruction further

controlling said data registers to move data stored in said second data register into said second data register with said second write priority, said move thereby having a higher write priority than said storing of said second result whereby said second data register stores data unchanged by said second instruction.

14. The data processing apparatus of claim 12, wherein:

said status register sets a negative status bit when said second result is negative.

15. The data processing apparatus of claim 12, wherein:

said status register sets a carry status bit when said second result generates a carry out signal.

16. The data processing apparatus of claim 12, wherein:

said status register sets an overflow status bit when said second result generates an overflow at said output.

17. The data processing apparatus of claim 12, wherein:

said status register sets a zero status bit when said second result is zero.

18. The data processing apparatus of claim 12, wherein:

said status register includes a plurality of status bits;

said instruction decode logic response to said second instruction setting each of said plurality of status bits in said status register corresponding to said second result;

said first instruction includes an indication of a set of said status bits upon which said conditional move is conditional; and

said instruction decode circuit in response to said first instruction controlling said plurality of data registers to conditionally move predetermined data into said first designated destination data register if said set of status bits indicated in said first instruction have a predetermined state.

19. The data processing apparatus of claim 11, further comprising:

a memory for storing data at a plurality of memory locations;

an address unit connected to said instruction decode circuit and said memory for generating an address for accessing said memory; and

said instruction decode circuit in response to said first instruction

controlling said address generator and said data registers to conditionally move predetermined data into said first data register by accessing an address via said address unit and transferring data stored in a memory location corresponding to said address to said first data register.

20. The data processing apparatus of claim 11, wherein:

said instruction decode circuit in response to said first instruction

controlling said data registers to conditionally move data stored a third data register to said first data register.

21. An data processing system comprising:

an data system bus transferring data and addresses;

a system memory connected to said data system bus, said system memory storing data and transferring data via said data system bus;

an data processor circuit connected to said data system bus, said data processor circuit including

a plurality of data registers,

a status register storing at least one status bit,

an arithmetic logic unit having first and second inputs and an output coupled to said plurality of data registers, said arithmetic logic unit performing an arithmetic or logical operation upon data received at said first and second inputs and generating a result at said output, and

an instruction logic circuit connected to said plurality of data registers, said status register and said arithmetic logic unit, said instruction logic circuit controlling said plurality of data registers, said status register and said arithmetic logic unit in response to a received instruction, said instruction logic circuit in response to a first instruction

controlling said arithmetic logic unit to form a first combination of inputs from first designated source data registers and store a first result in a first designated destination data register with a first write priority, and

controlling said plurality of data registers to conditionally move predetermined data into said first designated destination data register if said at least one status bit in said status register has a predetermined state with a second write priority, said second write priority of said conditional move being higher than said first write priority of said first combination of inputs of said arithmetic logic unit whereby said first designated destination data register stores said predetermined data if said at least one status register has said predetermined state or said result of said first combination if said at least one status register does not have said predetermined state.

22. The data processing system of claim 21, wherein:

said data processor circuit wherein

said instruction decode logic in response to a second instruction

controlling said arithmetic logic unit to form a second combination of inputs from designated source data registers and store a second result in a second designated destination data register with said first write priority, and

setting said at least one status bit in said status register corresponding to said second result.

23. The data processing system of claim 22, wherein:

said data processor circuit wherein

said instruction decode logic in response to a second instruction further

controlling said data registers to move data stored in said second data register into said second data register with said second write priority, said move thereby having a higher write priority than said storing of said second result whereby said second data register stores data unchanged by said second instruction.

24. The data processing system of claim 22, wherein:

said data processor circuit wherein

said status register sets a negative status bit when said second result is negative.

25. The data processing system of claim 22, wherein:

said data processor circuit wherein

said status register sets a carry status bit when said second result generates a carry out signal.

26. The data processing system of claim 22, wherein:

said data processor circuit wherein

said status register sets an overflow status bit when said second result generates an overflow at said output.

27. The data processing system of claim 22, wherein:

said data processor circuit wherein

said status register sets a zero status bit when said second result is zero.

28. The data processing system of claim 22, wherein:

said data processor circuit wherein

said status register includes a plurality of status bits,

said instruction decode logic in response to said second instruction setting each of aid plurality of status bits in said status register corresponding to said second result;

said first instruction includes an indication of a set of said status bits upon which said conditional move is conditional, and

said instruction decode circuit in response to said first instruction controlling said plurality of data registers to conditionally move predetermined data into said first designated destination data register if said set of status bits indicated in said first instruction have a predetermined state.

29. The data processing system of claim 21, wherein:

said data processor circuit further including

a memory for storing data at a plurality of memory locations,

an address unit connected to said instruction decode circuit and said memory for generating an address for accessing said memory, and

said instruction decode circuit in response to said first instruction

controlling said address generator and said data registers to conditionally move predetermined data into said first data register by accessing an address via said address unit and transferring data stored in a memory location corresponding to said address to said first data register.

30. The data processing system of claim 21, wherein:

said data processor circuit wherein

said instruction decode circuit in response to said first instruction

controlling said data registers to conditionally move data stored a third data register to said first data register.

31. The data processing system of claim 21, wherein:

said data processor circuit further includes

a plurality of data memories connected to said data processor circuit,

an instruction memory supplying instructions to said data processor circuit, and

a transfer controller connected to said data system bus, each of said data memories and said instruction memory controlling data transfer between said system memory and said plurality of data memories and between said system memory and said instruction memory.

32. The data processing system of claim 31, wherein:

said data processor circuit further includes

at least one additional data processor circuit identical to said data processor circuit,

a plurality of additional data memories connected to each additional data processor circuit,

an additional instruction memory supplying instructions to each additional data processor circuit, and

said transfer controller is further connected to each of said additional data memories and each said additional instruction memory controlling data transfer between said system memory and said each of said additional data memories and between said system memory and each said additional instruction memory.

33. The data processing system of claim 32, wherein:

said data processor circuit including said data processor circuit, said data memories, said instruction memories, each of said additional data processor circuits, each of said additional data memories, each additional instruction memory and said transfer controller are formed on a single integrated circuit.

34. The data processing system of claim 31, wherein:

said data processor circuit further includes

a master data processor,

a plurality of master data memories connected to said master data processor,

at least one master instruction memory supplying instructions to said master data processor, and

said transfer controller is further connected to each of said master data memories and each said master instruction memory controlling data transfer between said system memory and said each of said master data memories and between said system memory and each said master instruction memory.

35. The data processing system of claim 34, wherein:

said data processor circuit including said data processor circuit, said data memories, said instruction memories, said master data processor, each of said master data memories, each master instruction memory and said transfer controller are formed on a single integrated circuit.

36. The data processor system of claim 21, wherein:

said system memory consists of an image memory storing image data in a plurality of pixels; and

said data processor system further comprising;

an image display unit connected to said image memory generating a visually perceivable output of an image consisting of a plurality of pixels stored in said image memory.

37. The data processor system of claim 36, further comprising:

a palette forming a connection between said image memory and said image display unit, said palette transforming pixels recalled from said image memory into video signals driving said image display unit;

and wherein said data processor circuit further includes

a frame controller connected to said palette controlling said palette transformation of pixels into video signals.

38. The data processor system of claim 21, wherein:

said system memory consists of an image memory storing image data in a plurality of pixels; and

said data processor system further comprising;

a printer connected to said image memory generating a printed output of an image consisting of a plurality of pixels stored in said image memory.

39. The data processor system of claim 38, wherein:

said printer consists of a color printer.

40. The data processor system of claim 38, further comprising:

a printer controller forming a connection between said image memory and said printer, said printer controller transforming pixels recalled from said image memory into print signals driving said printer;

and wherein said data processor circuit further includes

a frame controller connected to said print controller controlling said print controller transformation of pixels into print signals.

41. The data processor system of claim 21, wherein:

said system memory consists of an image memory storing image data in a plurality of pixels; and

said data processor system further comprising;

an imaging device connected to said image memory generating an image signal input.

42. The data processor system of claim 41, further comprising:

an image capture controller forming a connection between said imaging device and said image memory, said image capture controller transforming said image signal into pixels supplied for storage in said image memory;

and wherein said data processor circuit further includes

a frame controller connected to said image capture controller controlling said image capture controller transformation of said image signal into pixels.

43. The data processor system of claim 21, further comprising:

a modem connected to said data system bus and to a communications line.

44. The data processor system of claim 21, further comprising:

a host processing system connected to said data system bus.

45. The data processor system of claim 44, further comprising:

a host system bus connected to said host processing system transferring data and addresses; and

at least one host peripheral connected to said host system bus.

46. A method of conditional data processing operation comprising the steps of:

a) setting a condition to either a first state or a second state;

b) providing a first instruction type including

an arithmetic logic unit code field indicating a first arithmetic/logical operation,

a first source field indicating a first source data register from among a plurality of data registers,

a second source field indicating a second source data register from among a plurality of data registers,

a destination field indicating a first destination data register from among a plurality of data registers,

at least one data transfer source field indicating a source of predetermined data for a first data transfer,

a data transfer destination field indicating a second destination data register from among a plurality of data registers,

a condition field indicating a state of said condition upon which a data transfer is conditional;

c) specifying an if-then-else instruction in said first instruction type having said destination field indicating said first destination data register as a common destination data register and said data transfer destination field indicating said second destination data register as said common destination data register; and

d) executing said if-then-else instruction by

performing said first arithmetic/logical operation on data from said first and second source data registers and storing a first result in said common destination data register with a first write priority, and

conditionally performing said first data transfer of said predetermined data into said common destination data register if said condition has said first state with a second write priority, said second write priority being higher than said first write priority thereby storing said predetermined data in said common destination data register if said condition has said first state or storing said first result of said first arithmetic/logical operation in said common destination data register if said condition does not have said first state.

47. The method of claim 46, wherein:

said step of setting a condition in either a first state or a second state includes

specifying a second instruction including a second arithmetic logic operation having third and fourth source data registers and a third destination data register,

executing said second instruction by performing said second arithmetic/logical operation on data from said third and fourth source data registers and storing a second result in said third destination data register with said first write priority,

setting at least one status bit dependent upon said second result, and

storing said at least one status bit in a status register.

48. The method of claim 47, wherein:

said step of setting a condition in either a first state or a second state wherein said substep of specifying said second instruction includes specifying said second instruction as said first instruction type having a destination field indicating said third destination data register as a second common destination data register;

said step of setting a condition in either a first state or a second state further includes

specifying in said second instruction an unconditional second data transfer of data stored in said second common destination data into said second common destination data register,

executing said second instruction by transferring data stored in said second common destination data register into said second common destination data register with said second write priority, said second data transfer operation thereby having a higher write priority than said storing of said second result whereby said second common destination data register stores unchanged data.

49. The method of claim 48, wherein:

said step of providing a first instruction type further includes a data transfer conditional field having either a first state indicating a conditional data transfer or a second state indicating an unconditional data transfer

said step of specifying said if-then-else instruction includes providing said data transfer conditional field in said first state; and

said step of specifying said second instruction employs said first instruction type and provides said data transfer conditional field in said second state.

50. The method of claim 47, wherein:

said step of setting a condition in either a first state or a second state wherein

said at least one status bit includes a negative status bit set to said first state if said second result is negative and set to said second state if said second result is not negative.

51. The method of claim 47, wherein:

said step of setting a condition in either a first state or a second state wherein

said at least one status bit includes a carry out status bit set to said first state if said second result generates a carry out and set to said second state if said second result does not generate a carry out.

52. The method of claim 47, wherein:

said step of setting a condition in either a first state or a second state wherein

said at least one status bit includes an overflow status bit set to said first state if said second result generates an overflow and set to said second state if said second result does not generate an overflow.

53. The method of claim 47, wherein:

said step of setting a condition in either a first state or a second state wherein

said at least one status bit includes a zero status bit set to said first state if said second result is zero and set to said second state if said second result is not zero.

54. The method of claim 47, wherein:

said step of setting a condition in either a first state or a second state further includes

setting a plurality of status bits dependent upon said second result, and

storing said plurality of status bits in said status register;

said step of providing said first instruction type includes said condition field indicating said state of said condition as a predetermined state of each status bit of a specified set of said plurality of status bits; and

said step of conditionally transferring predetermined data into said common destination data register if said condition has said first state includes testing said specified set of said plurality of said status bits of said condition field and conditionally transferring said predetermined data into said common destination data register if and only if each status bit in said selected set of said plurality of status bits has said predetermined state of said condition.

55. The method of claim 54, wherein:

said plurality of status bits consists of a negative status bit, a carry out status bit, an overflow status bit and a zero status bit;

said condition field of said first instruction type consists of 4 bits coding the following sixteen combinations of conditions

1) unconditional, in which the data transfer takes place regardless of the condition of said status bits,

2) positive, in which the data transfer takes place if and only if (Not N AND Not Z) is true,

3) lower than or same, in which the data transfer takes place if and only if (Not C OR Z) is true,

4) higher than, in which the data transfer takes place if and only if (C AND Not Z) is true,

5) less than, in which the data transfer takes place if and only if ((N AND Not V) OR (Not N AND V)) is true,

6) less than or equal to, in which the data transfer takes place if and only if ((N AND Not V) OR (Not N AND V) OR Z) is true,

7) greater than or equal to, in which the data transfer takes place if and only if ((N AND V) OR (Not N AND Not V)) is true,

8) greater than, in which the data transfer takes place if and only if ((N AND V AND Not Z) OR (Not N AND Not V AND Not Z)) is true,

9) lower than, carry, in which the data transfer takes place if and only if C is true,

10) higher than or same, no carry, in which the data transfer takes place if and only if (Not C) is true,

11) equal, zero, in which the data transfer takes place if and only if Z is true,

12) not equal, not zero, in which the data transfer takes place if and only if (Not Z) is true,

13) overflow, in which the data transfer takes place if and only if V is true,

14) no overflow, in which the data transfer takes place if and only if (Not V) is true,

15) negative, in which the data transfer takes place if and only if N is true, and

16) non-negative, in which the data transfer takes place if and only if (Not N) is true,

where;

N is the negative status bit;

C is the carry out status bit;

V is the overflow status bit; and

Z is the zero status bit.

56. The method of claim 46, wherein:

said step of providing a first instruction type includes providing said at least one data transfer source field indicating a predetermined memory location of a memory as said source of said predetermined data for said first data transfer; and

said step of conditionally transferring predetermined data into said common destination data register transfers said predetermined data from said predetermined memory location to said common destination data register.

57. The method of claim 46, wherein:

said step of providing a first instruction type includes providing said at least one data transfer source field indicating a third source data register as said source of said predetermined data for said first data transfer; and

said step of conditionally transferring predetermined data into said common destination data register transfers said predetermined data from said third source data register to said common destination data register.

58. A data processing apparatus comprising:

a plurality of data registers;

a status register storing at least one status bit;

an arithmetic logic unit having first and second inputs and an output coupled to said plurality of data registers, said arithmetic logic unit performing an arithmetic or logical operation upon data received at said first and second inputs and generating a result at said output;

a source instructions including at least one if-then-else instruction having a first instruction type, said first instruction type including

an arithmetic logic unit code field indicating a first arithmetic/logical operation,

a first source field indicating a first source data register from among a plurality of data registers,

a second source field indicating a second source data register from among a plurality of data registers,

a destination field indicating a first destination data register from among a plurality of data registers,

at least one data transfer source field indicating a source of predetermined data for a first data transfer,

a data transfer destination field indicating a second destination data register from among a plurality of data registers,

a condition field indicating a predetermined state of said at least one status bit upon which a data transfer is conditional,

said at least one if-then-else instruction having said destination field indicating said first destination data register as a common destination data register and said data transfer destination field indicating said second destination data register as said common destination data register;

an instruction logic circuit connected to said plurality of data registers, said status register, said arithmetic logic unit and said source of instructions, said instruction logic circuit controlling said plurality of data registers, said status register and said arithmetic logic unit in response to a received instruction, said instruction logic circuit in response to an if-then-else instruction

controlling said arithmetic logic unit to form a first combination of said first and second source data registers corresponding to said specified first arithmetic/logical operation and store a first result in said common destination data register with a first write priority, and

controlling said plurality of data registers to conditionally transfer predetermined data into said common destination data register if said at least one status bit in said status register has said predetermined state with a second write priority, said second write priority being higher than said first write priority whereby said common destination data register stores said predetermined data if said at least one status register has said predetermined state or said first result if said at least one status register does not have said predetermined state.

59. The data processing apparatus of claim 58, wherein:

said source instructions includes a second instruction specifying a second arithmetic logic operation having third and fourth source data registers and a third destination data register; and

said instruction decode logic in response to a second instruction

controlling said arithmetic logic unit to form a second combination of said third and fourth source data registers corresponding to said specified second arithmetic/logical operation and store a second result in said third destination data register with a first write priority, and

setting said at least one status bit in said status register corresponding to said second result.

60. The data processing apparatus of claim 59, wherein:

said second instruction

is of said first instruction type and further includes a destination field indicating said third destination data register as a second common destination data register, and

specifies an unconditional second data transfer operation of data stored in said second common destination data into said second common destination data register with said second write priority;

said instruction decode logic in response to a second instruction further

controlling said data registers to transfer data stored in said second common destination data register into said second common destination data register with said second write priority, said second data transfer operation thereby having a higher write priority than said storing of said second result whereby said second common destination data register stores data unchanged by said second instruction.

61. The data processing apparatus of claim 60, wherein:

said first instruction type further includes a data transfer conditional field having either a first state indicating a conditional data transfer or a second state indicating an unconditional data transfer;

said if-then-else instruction includes providing said data transfer conditional field in said first state; and

said second instruction employs said first instruction type and provides said data transfer conditional field in said second state.

62. The data processing apparatus of claim 59, wherein:

said status register sets a negative status bit when said second result is negative.

63. The data processing apparatus of claim 59, wherein:

said status register sets a carry status bit when said second result generates a carry out signal.

64. The data processing apparatus of claim 59, wherein:

said status register sets an overflow status bit when said second result generates an overflow at said output.

65. The data processing apparatus of claim 59, wherein:

said status register sets a zero status bit when said second result is zero.

66. The data processing apparatus of claim 59, wherein:

said status register includes a plurality of status bits;

said instruction decode logic in response to said second instruction setting each of said plurality of status bits in said status register corresponding to said second result;

said if-then-else instruction specifies said condition as a predetermined state of each status bit of a specified set of said plurality of status bits; and

said instruction decode circuit in response to said if-then-else instruction controlling said plurality of data registers to conditionally transfer predetermined data into said common destination data register if and only if each status bit in said selected set of said plurality of status bits has said predetermined state of said condition.

67. The data processing apparatus of claim 66, wherein:

said plurality of status bits stored in said status register consists of a negative status bit, a carry out status bit, an overflow status bit and a zero status bit;

said condition field of said first instruction type consists of 4 bits coding the following sixteen combinations of conditions

1) unconditional, in which the data transfer takes place regardless of the condition of said status bits,

2) positive, in which the data transfer takes place if and only if (Not N AND Not Z) is true,

3) lower than or same, in which the data transfer takes place if and only if (Not C OR Z) is true,

4) higher than, in which the data transfer takes place if and only if (C AND Not Z) is true,

5) less than, in which the data transfer takes place if and only if ((N AND Not V) OR (Not N AND V)) is true,

6) less than or equal to, in which the data transfer takes place if and only if ((N AND Not V) OR (Not N AND V) OR Z) is true,

7) greater than or equal to, in which the data transfer takes place if and only if ((N AND V) OR (Not N AND Not V)) is true,

8) greater than, in which the data transfer takes place if and only if ((N AND V AND Not Z) OR (Not N AND Not V AND Not Z)) is true,

9) lower than, carry, in which the data transfer takes place if and only if C is true,

10) higher than or same, no carry, in which the data transfer takes place if and only if (Not C) is true,

11) equal, zero, in which the data transfer takes place if and only if Z is true,

12) not equal, not zero, in which the data transfer takes place if and only if (Not Z) is true,

13) overflow, in which the data transfer takes place if and only if V is true,

14) no overflow, in which the data transfer takes place if and only if (Not V) is true,

15) negative, in which the data transfer takes place if and only if N is true, and

16) non-negative, in which the data transfer takes place if and only if (Not N) is true,

where;

N is the negative status bit;

C is the carry out status bit;

V is the overflow status bit; and

Z is the zero status bit.

68. The data processing apparatus of claim 58, further comprising:

a memory for storing data at a plurality of memory locations;

an address unit connected to said instruction decode circuit and said memory for generating an address for accessing said memory;

said a first instruction type includes providing said at least one data transfer source field indicating a predetermined operation of said address unit for generating said address of said memory as said source of said predetermined data for said first data transfer; and

said instruction decode circuit in response to said if-then-else instruction

controlling said address generator and said data registers to conditionally transfer predetermined data into said common destination data register by accessing an address via said predetermined operation of said address unit and transferring data stored in a memory location corresponding to said address to said common destination data register.

69. The data processing apparatus of claim 58, wherein:

said first instruction type includes said at least one data transfer source field indicating a third source data register as said source of said predetermined data for said first data transfer; and

said instruction decode circuit in response to said if-then-else instruction

controlling said data registers to conditionally transfer data stored in said third source data register to said common destination data register.

70. An data processing system comprising:

an data system bus transferring data and addresses;

a system memory connected to said data system bus, said system memory storing data and transferring data via said data system bus;

an data processor circuit connected to said data system bus, said data processor circuit including

a plurality of data registers;

a status register storing at least one status bit;

an arithmetic logic unit having first and second inputs and an output coupled to said plurality of data registers, said arithmetic logic unit performing an arithmetic or logical operation upon data received at said first and second inputs and generating a result at said output;

a source instructions including at least one if-then-else instruction having a first instruction type, said first instruction type including

an arithmetic logic unit code field indicating a first arithmetic/logical operation,

a first source field indicating a first source data register from among a plurality of data registers,

a second source field indicating a second source data register from among a plurality of data registers,

a destination field indicating a first destination data register from among a plurality of data registers,

at least one data transfer source field indicating a source of predetermined data for a first data transfer,

a data transfer destination field indicating a second destination data register from among a plurality of data registers,

a condition field indicating a predetermined state of said at least one status bit upon which a data transfer is conditional,

said at least one if-then-else instruction having said destination field indicating said first destination data register as a common destination data register and said data transfer destination field indicating said second destination data register as said common destination data register;

an instruction logic circuit connected to said plurality of data registers, said status register, said arithmetic logic unit and said source of instructions, said instruction logic circuit controlling said plurality of data registers, said status register and said arithmetic logic unit in response to a received instruction, said instruction logic circuit in response to an if-then-else instruction

controlling said arithmetic logic unit to form a first combination of said first and second source data registers corresponding to said specified first arithmetic/logical operation and store a first result in said common destination data register with a first write priority, and

controlling said plurality of data registers to conditionally transfer predetermined data into said common destination data register if said at least one status bit in said status register has said predetermined state with a second write priority, said second write priority being higher than said first write priority whereby said common destination data register stores said predetermined data if said at least one status register has said predetermined state or said first result if said at least one status register does not have said predetermined state.

71. The data processing system of claim 70, wherein:

said data processor circuit wherein

said source instructions includes a second instruction specifying a second arithmetic logic operation having third and fourth source data registers and a third destination data register; and

said instruction decode logic in response to a second instruction

controlling said arithmetic logic unit to form a second combination of said third and fourth source data registers corresponding to said specified second arithmetic/logical operation and store a second result in said third destination data register with a first write priority, and

setting said at least one status bit in said status register corresponding to said second result.

72. The data processing system of claim 71, wherein:

said data processor circuit wherein

said second instruction

is of said first instruction type and includes a destination field indicating said third destination data register as a second common destination data register, and

specifies an unconditional second data transfer operation of data stored in said second common destination data into said second common destination data register with said second write priority;

said instruction decode logic in response to a second instruction further

controlling said data registers to transfer data stored in said second common destination data register into said second common destination data register with said second write priority, said second data transfer operation thereby having a higher write priority than said storing of said second result whereby said second common destination data register stores data unchanged by said second instruction.

73. The data processing system of claim 72, wherein:

said data processor circuit wherein

said first instruction type further includes a data transfer conditional field having either a first state indicating a conditional data transfer or a second state indicating an unconditional data transfer;

said if-then-else instruction includes providing said data transfer conditional field in said first state; and

said second instruction employs said first instruction type and provides said data transfer conditional field in said second state.

74. The data processing system of claim 71, wherein:

said data processor circuit wherein

said status register sets a negative status bit when said second result is negative.

75. The data processing system of claim 71, wherein:

said data processor circuit wherein

said status register sets a carry status bit when said second result generates a carry out signal.

76. The data processing system of claim 71, wherein:

said data processor circuit wherein

said status register sets an overflow status bit when said second result generates an overflow at said output.

77. The data processing system of claim 71, wherein:

said data processor circuit wherein

said status register sets a zero status bit when said second result is zero.

78. The data processing system of claim 71, wherein:

said data processor circuit wherein

said status register includes a plurality of status bits;

said instruction decode logic in response to said second instruction setting each of said plurality of status bits in said status register corresponding to said second result;

said if-then-else instruction specifies said condition as a predetermined state of each status bit of a specified set of said plurality of status bits; and

said instruction decode circuit in response to said if-then-else instruction controlling said plurality of data registers to conditionally transfer predetermined data into said common destination data register if and only if each status bit in said selected set of said plurality of status bits has said predetermined state of said condition.

79. The data processing system of claim 78, wherein:

said data processor circuit wherein

said plurality of status bits stored in said status register consists of a negative status bit, a carry out status bit, an overflow status bit and a zero status bit;

said condition field of said first instruction type consists of 4 bits coding the following sixteen combinations of conditions

1) unconditional, in which the data transfer takes place regardless of the condition of said status bits,

2) positive, in which the data transfer takes place if and only if (Not N AND Not Z) is true,

3) lower than or same, in which the data transfer takes place if and only if (Not C OR Z) is true,

4) higher than, in which the data transfer takes place if and only if (C AND Not Z) is true,

5) less than, in which the data transfer takes place if and only if ((N AND Not V) OR (Not N AND V)) is true,

6) less than or equal to, in which the data transfer takes place if and only if ((N AND Not V) OR (Not N AND V) OR Z) is true,

7) greater than or equal to, in which the data transfer takes place if and only if ((N AND V) OR (Not N AND Not V)) is true,

8) greater than, in which the data transfer takes place if and only if ((N AND V AND Not Z) OR (Not N AND Not V AND Not Z)) is true,

9) lower than, carry, in which the data transfer takes place if and only if C is true,

10) higher than or same, no carry, in which the data transfer takes place if and only if (Not C) is true,

11) equal, zero, in which the data transfer takes place if and only if Z is true,

12) not equal, not zero, in which the data transfer takes place if and only if (Not Z) is true,

13) overflow, in which the data transfer takes place if and only if V is true,

14) no overflow, in which the data transfer takes place if and only if (Not V) is true,

15) negative, in which the data transfer takes place if and only if N is true, and

16) non-negative, in which the data transfer takes place if and only if (Not N) is true,

where;

N is the negative status bit;

C is the carry out status bit;

V is the overflow status bit; and

Z is the zero status bit.

80. The data processing system of claim 70, wherein:

said data processor circuit further including

a memory for storing data at a plurality of memory locations,

an address unit connected to said instruction decode circuit and said memory for generating an address for accessing said memory, and

said a first instruction type includes providing said at least one data transfer source field indicating a predetermined operation of said address unit for generating said address of said memory as said source of said predetermined data for said first data transfer; and

said instruction decode circuit in response to said if-then-else instruction

controlling said address generator and said data registers to conditionally transfer predetermined data into said common destination data register by accessing an address via said predetermined operation of said address unit and transferring data stored in a memory location corresponding to said address to said common destination data register.

81. The data processing system of claim 70, wherein:

said data processor circuit wherein

said first instruction type includes said at least one data transfer source field indicating a third source data register as said source of said predetermined data for said first data transfer; and

said instruction decode circuit in response to said if-then-else instruction

controlling said data registers to conditionally transfer data stored in said third source data register to said common destination data register.

82. The data processing system of claim 70, wherein:

said data processor circuit further includes

a plurality of data memories connected to said data processor circuit,

an instruction memory supplying instructions to said data processor circuit, and

a transfer controller connected to said data system bus, each of said data memories and said instruction memory controlling data transfer between said system memory and said plurality of data memories and between said system memory and said instruction memory.

83. The data processing system of claim 82, wherein:

said data processor circuit further includes

at least one additional data processor circuit identical to said data processor circuit,

a plurality of additional data memories connected to each additional data processor circuit,

an additional instruction memory supplying instructions to each additional data processor circuit, and

said transfer controller is further connected to each of said additional data memories and each said additional instruction memory controlling data transfer between said system memory and said each of said additional data memories and between said system memory and each said additional instruction memory.

84. The data processing system of claim 83, wherein:

said data processor circuit including said data processor circuit, said data memories, said instruction memories, each of said additional data processor circuits, each of said additional data memories, each additional instruction memory and said transfer controller are formed on a single integrated circuit.

85. The data processing system of claim 82, wherein:

said data processor circuit further includes

a master data processor,

a plurality of master data memories connected to said master data processor,

at least one master instruction memory supplying instructions to said master data processor, and

said transfer controller is further connected to each of said master data memories and each said master instruction memory controlling data transfer between said system memory and said each of said master data memories and between said system memory and each said master instruction memory.

86. The data processing system of claim 85, wherein:

said data processor circuit including said data processor circuit, said data memories, said instruction memories, said master data processor, each of said master data memories, each master instruction memory and said transfer controller are formed on a single integrated circuit.

87. The data processor system of claim 70, wherein:

said system memory consists of an image memory storing image data in a plurality of pixels; and

said data processor system further comprising;

an image display unit connected to said image memory generating a visually perceivable output of an image consisting of a plurality of pixels stored in said image memory.

88. The data processor system of claim 87, further comprising:

a palette forming a connection between said image memory and said image display unit, said palette transforming pixels recalled from said image memory into video signals driving said image display unit;

and wherein said data processor circuit further includes

a frame controller connected to said palette controlling said palette transformation of pixels into video signals.

89. The data processor system of claim 70, wherein:

said system memory consists of an image memory storing image data in a plurality of pixels; and

said data processor system further comprising;

a printer connected to said image memory generating a printed output of an image consisting of a plurality of pixels stored in said image memory.

90. The data processor system of claim 89, wherein:

said printer consists of a color printer.

91. The data processor system of claim 89, further comprising:

a printer controller forming a connection between said image memory and said printer, said printer controller transforming pixels recalled from said image memory into print signals driving said printer;

and wherein said data processor circuit further includes

a frame controller connected to said print controller controlling said print controller transformation of pixels into print signals.

92. The data processor system of claim 70, wherein:

said system memory consists of an image memory storing image data in a plurality of pixels; and

said data processor system further comprising;

an imaging device connected to said image memory generating an image signal input.

93. The data processor system of claim 92, further comprising:

an image capture controller forming a connection between said imaging device and said image memory, said image capture controller transforming said image signal into pixels supplied for storage in said image memory;

and wherein said data processor circuit further includes

a frame controller connected to said image capture controller controlling said image capture controller transformation of said image signal into pixels.

94. The data processor system of claim 70, further comprising:

a modem connected to said data system bus and to a communications line.

95. The data processor system of claim 70, further comprising:

a host processing system connected to said data system bus.

96. The data processor system of claim 95, further comprising:

a host system bus connected to said host processing system transferring data and addresses; and

at least one host peripheral connected to said host system bus.