Method and apparatus for addressing a peripheral interface by mapping into memory address space
First Claim
1. An apparatus for transferring information across an interface between a first subsystem and a second subsystem of a system, wherein said first subsystem includes a programmable processor and a memory, said processor capable of executing memory reference instructions which reference by a memory address data stored in said memory, said apparatus comprising:
- A. address decoding means coupled to said processor, said address decoding means for detecting said memory address of said memory reference instructions which address a predetermined memory location in said memory;
B. interface control means coupled to said address decoding means and said processor, said interface control means responsive to said address decoding means when said address decoding means detects said memory reference instruction being executed which addresses said predetermined memory location for generating a strobe signal to said second subsystem and for receiving an acknowledge signal from said second subsystem;
C. a wait means coupled to said interface control means and said processor, said wait means responsive to said interface control means for generating a wait signal to place said processor in a wait state at the time said interface control means generates said strobe signal and for removing said processor from said wait state upon receipt of said acknowledge signal by said interface control means from said second subsystem; and
D. transceiver means coupled to said interface control means, said processor and said second subsystem, said transceiver means for receiving data from said processor during the execution of said write memory reference instruction and transmitting the data to said second subsystem and for receiving data from said second subsystem and transmitting the data to said processor during the execution of said read memory reference instructionwhereby said first subsystem can transfer information to or from said second subsystem by said processor executing memory reference instructions addressing said predetermied memory locations thereby effectively mapping said interface into the address space of said memory.
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Abstract
A method and apparatus for addressing a peripheral interface by mapping into the memory address space of a processor contained in a peripheral controller. The processor in the peripheral controller initializes interface logic within the peripheral controller and in the host system peripheral interface logic to which the peripheral controller is attached to either transmit or receive a block of data. Once initialized, units of data are transmitted across the interface between the peripheral controller and host system using a strobe and acknowledge signal to indicate when data can be taken or placed on data lines. The processor is placed in a wait state as each unit of data is transferred and a watch dog timer is provided to detect any transfer that is not completed within the normal response time of the interface.
45 Citations
16 Claims
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1. An apparatus for transferring information across an interface between a first subsystem and a second subsystem of a system, wherein said first subsystem includes a programmable processor and a memory, said processor capable of executing memory reference instructions which reference by a memory address data stored in said memory, said apparatus comprising:
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A. address decoding means coupled to said processor, said address decoding means for detecting said memory address of said memory reference instructions which address a predetermined memory location in said memory; B. interface control means coupled to said address decoding means and said processor, said interface control means responsive to said address decoding means when said address decoding means detects said memory reference instruction being executed which addresses said predetermined memory location for generating a strobe signal to said second subsystem and for receiving an acknowledge signal from said second subsystem; C. a wait means coupled to said interface control means and said processor, said wait means responsive to said interface control means for generating a wait signal to place said processor in a wait state at the time said interface control means generates said strobe signal and for removing said processor from said wait state upon receipt of said acknowledge signal by said interface control means from said second subsystem; and D. transceiver means coupled to said interface control means, said processor and said second subsystem, said transceiver means for receiving data from said processor during the execution of said write memory reference instruction and transmitting the data to said second subsystem and for receiving data from said second subsystem and transmitting the data to said processor during the execution of said read memory reference instruction whereby said first subsystem can transfer information to or from said second subsystem by said processor executing memory reference instructions addressing said predetermied memory locations thereby effectively mapping said interface into the address space of said memory. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method for transferring information across an interface between a first subsystem and a second subsystem of a system, wherein said first subsystem includes a programmable processor, an interface control means and a memory, said processor capable of executing memory reference instructions which reference data stored in said memory by a memory address, said method comprising the steps of:
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1. detecting the execution of a memory reference instruction which addresses a predetermined memory location in said memory by use of an address decoding means coupled to said processor; 2. indicating to said second subsystem whether data is to be transmitted from said first subsystem to said second subsystem or from second subsystem to said first subsystem as a function of whether a write or a read memory reference instruction is being executed by said processor; 3. generating a strobe signal to said second subsystem in response to said address decoding means detecting the execution of said memory reference instruction which addresses said predetermined memory location;
4. placing said processor in a wait state in response to a wait signal received from said interface control means when said interface control means generates said strobe signal;5. waiting for receipt of an acknowledge signal from said second subsystem by said interface control means, said acknowledge signal being generated by said second subsystem in response to said second subsystem receiving data from or transmitting data to said first subsystem; 6. transmitting data from said processor to said second subsystem across said interface if said write memory reference instruction is being executed by said processor; 7. receiving information from said second subsystem and transferring it to said processor if said read memory reference instruction is being executed by said processor upon receipt of said acknowledge signal from said second subsystem; 8. removing said processor from said wait state upon receipt by said interface control means of said acknowledge signal from said second subsystem; and - View Dependent Claims (13)
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12. continuing the execution of said processor memory reference instructions
whereby said first subsystem can transfer information to or from second subsystem by said processor executing memory reference instructions addressing said predetermined memory locations thereby effectively mapping said interface into the address space of said memory.
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14. A method for transferring information across an interface between a first subsystem and a second subsystem of a system wherein said first subsystem includes a programmable processor and a first memory, said processor capable of executing memory reference instructions which reference data stored in said first memory by a memory address, said method comprising the steps of:
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1. setting a control/data line to a control state and a direction line to an out state by executing an I/O instruction to a predetermined I/O port address; 2. sending a direct memory access select information to said second subsystem by referencing a predetermined memory location in said first memory; 3. setting said control/data line to a data state and said direction line to the out state by executing an input/output operation to said predetermined I/O port address; 4. sending the address of a first location of a block of memory locations in a second memory contained in said second subsystem to said second subsystem by executing a memory reference instruction addressing said predetermined memory address; 5. initializing a pointer to a first location in said first memory;
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15. loading a counter with a count of the number of units of data to be transferred between said first subsystem and said second subsystem;
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7. if a write operation is to be performed from said first subsystem to said second subsystem, accessing the next unit of data in the said first memory and executing a memory reference instruction addressing said predetermined memory location or, if a read operation is to be performed from said second subsystem to said first subsystem, executing a memory reference instruction addressing said predetermined memory location and writing said received unit of data into the next memory location addressed by said pointer to said first memory; 8. incrementing said pointer; 9. decrementing the count of the number of units of data to be transferred; 10. returning to step 7, if all units of data have not been transferred between said first subsystem and second subsystem; and
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16. continuing, if all units of data have been transferred;
whereby said first subsystem can transfer information to or from said second subsystem by said processor executing memory reference instructions addressing said predetermined memory locations thereby effectively mapping said interface into the address space of said first memory.
Specification