AT90S1200 Просмотр технического описания (PDF) - Atmel Corporation

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AT90S1200

8-Bit Microcontroller with 1K bytes In-System Programmable Flash

Atmel Corporation 

I/O Direct

Operands are contained in register r (Rr) and d (Rd). The result is stored in register d

(Rd).

Figure 9. I/O Direct Addressing

Operand address is contained in 6 bits of the instruction word. n is the destination or

source register address.

Relative Program Addressing, Figure 10. Relative Program Memory Addressing

RJMP and RCALL

Program execution continues at address PC + k + 1. The relative address k is -2048 to

2047.

Subroutine and Interrupt

Hardware Stack

The AT90S1200 uses a 3 level deep hardware stack for subroutines and interrupts. The

hardware stack is 9 bits wide and stores the Program Counter (PC) return address while

subroutines and interrupts are executed.

RCALL instructions and interrupts push the PC return address onto stack level 0, and

the data in the other stack levels 1 - 2 are pushed one level deeper in the stack. When a

RET or RETI instruction is executed the returning PC is fetched from stack level 0, and

the data in the other stack levels 1 - 2 are popped one level in the stack.

If more than three subsequent subroutine calls or interrupts are executed, the first val-

ues written to the stack are overwritten.

8 AT90S1200

0838H–AVR–03/02

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