Microcontroller
View Patent ↗A peripheral circuit control register has a plurality of bits corresponding respectively to peripheral resources. A decoder activates an access signal to the peripheral resource at an access destination when the bit corresponding to the peripheral resource at the access destination in the peripheral circuit control register is under a set state in response to occurrence of access to any of the peripheral resources by a CPU. A functional specification of an evaluation chip can be made equivalent to those of product chips and development of a wrong user program can be prevented by setting in advance the bits of the peripheral circuit control register corresponding to the peripheral resources mounted to the product chip to the set state.
1. A microcontroller being configured as a common evaluation chip that comprehensively includes functional specifications of a plurality of product chips, said microcontroller comprising:
a processing circuit operating in accordance with a program;
a plurality of peripheral circuits;
a peripheral circuit control register having a plurality of bits corresponding to said plurality of peripheral circuits, respectively, among the plurality of bits a bit corresponding to a peripheral circuit mounted on the microcontroller and associated with a functional specification of one of the product chips being an object of program development is set under a set state and a bit corresponding to a peripheral circuit not associated with a functional specification of one of the product chips is set under a reset state, via an access by said processing circuit; and
an access control circuit activating an access signal to the peripheral circuit to which the access by said processing circuit occurs when one of the bits in said peripheral circuit control register corresponding to the peripheral circuit is under a set state and not activating the access signal to the peripheral circuit to which the access by said processing circuit occurs when one of the bits in said peripheral circuit control register corresponding to the peripheral circuit is under a reset state, when the access to any of said peripheral circuits by said processing circuit occurs.
2. The microcontroller according to claim 1 , wherein said access control circuit includes:
a decode circuit activating any of access signals to said plurality of peripheral circuits in accordance with an access destination address representing an access destination of said processing circuit; and
a plurality of mask circuits arranged to correspond to said plurality of peripheral circuits, respectively, and masking the access signals to corresponding peripheral circuits when corresponding bits in said peripheral circuit control register are under a reset state.
3. The microcontroller according to claim 1 , wherein
said access control circuit does not activate the access signal to said peripheral circuit control register even when the access to said peripheral circuit control register by said processing circuit occurs in a normal operation mode in which said processing circuit operates in accordance with a user program, and activates the access signal to said peripheral circuit control register in response to occurrence of the access to said peripheral circuit control register by said processing circuit in a privileged operation mode in which said processing circuit operates in accordance with a program different from said user program.
4. The microcontroller according to claim 3 , further comprising:
a memory; and a memory control register designating an access area of said memory, wherein the access control circuit activates an access signal to said memory in response to occurrence of access to said memory by said processing circuit when an access destination is contained in the access area designated by said memory control register.
5. The microcontroller according to claim 4 , wherein:
said memory control register has first and second registers respectively designating a start address and an end address of the access area of said memory; and
said access control circuit has a comparison circuit respectively comparing an access destination address representing an access destination of said processing circuit with the addresses designated by said first and second registers, and then activating the access signal to said memory when said access destination address is greater than or equal to the address designated by said first register and is smaller than or equal to the address designated by said second register.
6. The microcontroller according to claim 4 , wherein:
said memory control register has a first register designating a start address of the access area of said memory; and
said access control circuit has a comparison circuit respectively comparing an access destination address representing an access destination of said processing circuit with the address designated by said first register and an end address of said memory, and then activating the access signal to said memory when said access destination address is greater than or equal to the address designated by said first register and is smaller than or equal to the end address of said memory.
7. The microcontroller according to claim 4 , wherein:
said memory control register has a second register designating an end address of the access area of said memory; and
said access control circuit has a comparison circuit respectively comparing an access destination address representing an access destination of said processing circuit with a start address of said memory and the address designated by said second register, and then activating the access signal to said memory when said access destination address is greater than or equal to the start address of said memory and is smaller than or equal to the address designated by said second register.
8. The microcontroller according to claim 4 , wherein in said privileged operation mode, said access control circuit activates the access signal to said memory control register in response to occurrence of access to said memory control register by said processing circuit.
9. The microcontroller according to claim 3 , wherein the plurality of peripheral circuits output first interrupt requests, respectively, and the microcontroller further comprises:
an interrupt request control register designating a correspondence relation among the first interrupt requests from said plurality of peripheral circuits and a plurality of second interrupt requests; and
an interrupt request substitution circuit substituting said plurality of second interrupt requests for said first interrupt requests from said plurality of peripheral circuits to output said second interrupt requests, in accordance with the correspondence relation designated by said interrupt request control register;
wherein the processing circuit executes any of a plurality of interrupt processing corresponding to said plurality of second interrupt requests in accordance with said plurality of second interrupt requests.
10. The microcontroller according to claim 9 , wherein:
said interrupt request control register has a plurality of sub-registers arranged to respectively correspond to said plurality of second interrupt requests, and respectively designating any of the first interrupt requests from said plurality of peripheral circuits; and
said interrupt request substitution circuit has a plurality of selection circuits arranged to respectively correspond to said plurality of second interrupt requests, and outputting the first interrupt requests designated by the corresponding sub-registers as corresponding second interrupt requests.
11. The microcontroller according to claim 9 , wherein:
said interrupt request control register has a plurality of sub-registers arranged to respectively correspond to the first interrupt requests from said plurality of peripheral circuits, and having a plurality of bits corresponding to said plurality of second interrupt requests, respectively; and
said interrupt request substitution circuit includes
a plurality of assignment circuits arranged to respectively correspond to the first interrupt requests from said plurality of peripheral circuits, and outputting the corresponding first interrupt request as a third interrupt request corresponding to the bit under a set state in the corresponding sub-register among a plurality of third interrupt requests respectively corresponding to said plurality of second interrupt requests, and
a plurality of synthesis circuits arranged to respectively correspond to said plurality of second interrupt requests, and commonly outputting a plurality of third interrupt requests corresponding to a same second interrupt request, among the third interrupt requests from said plurality of assignment circuits as a corresponding second interrupt request.
12. The microcontroller according to claim 9 , wherein the access control circuit fixes an access signal to said interrupt request control register to an inactive level in the normal operation mode in which said processing circuit operates in accordance with the user program, and activates the access signal to said interrupt request control register in response to occurrence of access to said interrupt request control register by said processing circuit in the privileged operation mode in which said processing circuit operates in accordance with a program different from the user program.