Microprocessor for selectively performing cold and warm starts

• US 5,361,365 A
• Filed: 02/23/1993
• Issued: 11/01/1994
• Est. Priority Date: 11/06/1989
• Status: Expired due to Term

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Hirano, Takaaki, Hashimoto, Yoshinori
• Primary Examiner(s): Ray, Gopal C.
• Application Number:
  US08/024,104
• Time in Patent Office: 616 Days
• Field of Search: 395/775, 395/425, 395/725, 395/700, 395/934, 371/11.3, 380/4
• US Class Current: 713/1
• CPC Class Codes: G06F 9/32 Address formation of the next instruction, e.g. by incrementing the instruction counter G06F9/38 takes precedence
• CPC Class Codes: G06F 9/4401 Bootstrapping security arrangements therefor G06F21/57

Abstract

Upon power-on, a microprocessor is reset and initiates a cold start initialization program stored in ROM for initializing the microprocessor and associated peripherals. Thereafter, externally input control signals to the microprocessor indicate a desirable initialization operation for a warm start when the microprocessor is subsequently reset by an operator. A reset address generating circuit generates (1) a first address setting signal to set a first starting address of the initialization program for a cold start when receiving the reset signal at a power-ON or (2) a second address setting signal to set a second starting address of the initialization program corresponding to the warm start after the power-ON when receiving both a reset signal and a control signal generated externally by a user. A program counter is then set to an address corresponding to the inputted address setting signal. The microprocessor reads and executes initialization programs based on instructions in memory addressed by the program counter.

Claims

1. A microprocessor for selectively executing different initialization programs, comprising:

a memory for storing at least first and second initialization programs, the first initialization program corresponding to a first resetting operation occurring simultaneously with power-on of the microprocessor and having a first starting address, and the second initialization program corresponding to a second resetting operation of the microprocessor subsequent to power on and having a second starting address;

a program counter for providing one of the first and second addresses to the memory to access a corresponding first or second initialization program to be executed;

an address generator providing signals corresponding to the first starting address based on a power-on reset signal supplied thereto to set the contents of the program counter to the first starting address and signals corresponding to the second starting address based on received reset and control signals supplied thereto to set the contents of the program counter to the second starting address, the control signals being externally actuated by a user; and

a logic unit for executing one of the first and second initialization programs based on the starting address generated by the program counter.

2. A microprocessor according to claim 1, in which the address generator includes a plurality of bit control circuits, each of the plurality of bit control circuits generates one bit of the first and second starting addresses.

3. A microprocessor according to claim 2, in which the address generator includes an address set timing signal generating circuit for supplying an address set timing signal to each of the plurality of bit control circuits to cause the plurality of bit control circuits to respectively generate the first and second starting addresses.

4. A microprocessor according to claim 1, in which the program counter includes a plurality of internal bit registers for receiving one of the first and second starting addresses generated by the address generator.

5. A microprocessor according to claim 1, in which the logic unit includes an arithmetic logic unit, a register file, a command decoder and a command register.

6. The microprocessor according to claim 1, wherein the first resetting operation corresponds to a cold start initialization program stored at the first start address, and the second resetting operation corresponds to a warm start reinitialization program stored at the second start address.

7. The microprocessor according to claim 1, wherein the externally produced control signals are specified and input by a user through a data input/output terminal to selectively determine the second start address to be set by the address generator.

8. The microprocessor according to claim 1, further comprising:

an automatic reset circuit for providing an automatic reset signal corresponding to the first start address, and

a reset address register for receiving the automatic reset signal and control signals selectively generated by a user and corresponding to the second address,

wherein the address generator generates the address selection signal based on the reset signal and signals received from the reset address register.

9. The microprocessor according to claim 1, wherein the address generator includes:

an address timing signal generator for producing an address timing signal, and

a plurality of individual bit control circuits each receiving the reset signal, the address timing signal and corresponding individual control signals, each bit control circuit generating an address setting signal associated with the corresponding individual control signal when the reset signal and address timing signal achieve a predetermined logic state.

10. The microprocessor according to claim 9, wherein the program counter includes a plurality of internal bit registers, each internal bit register corresponding to one of the bit control circuits and receiving the reset signal and the associated address setting signal generated by the corresponding bit control circuit, wherein the second start address is selectively preset via the individual control signals input to the individual bit control circuits.

11. The microprocessor according to claim 10, wherein the address setting signal from an individual bit control circuit sets the address bits for plural adjacent internal bit registers.

12. The microprocessor according to claim 10, wherein the address setting signal from an individual bit control circuit controls the address value for plural internal bit registers.