GMS81032 datasheet(25/101 Pages) HYNIX

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Chapter 2. Function Description

2.1.1 A register

- 8bit Accumulator.

- In the case of 16-bit operation, compose the lower 8-bit of A, upper 8bit in Y (16-bit

Accumulator)

- In the case of multiplication instruction, execute as a multiplier register. After

multiplication operation, the lower 8-bit of the result enters. (Y*A ¡æ YA)

- In the case of division instruction, execute as the lower 8-bit of dividend. After

division operation, quotient enters.

2.1.2 X register

- General-purpose 8-bit register

- In the case of index addressing mode within direct page(RAM area), execute as

index register.

- In the case of division instruction, execute as register.

2.1.3 Y register

- General-purpose 8-bit register

- In the case of index addressing mode, execute as index register

- In the case of 16-bit operation instruction, execute as the upper 8-bit of YA (16-bit

accumulator).

- In the case of multiplication instruction, execute as a multiplicand register. After

multiplication operation, the upper 8-bit of the result enters.

- In the case of division instruction, execute as the upper 8-bit of dividend. After

division operation, remains enters.

- Can be used as loop counter of conditional branch command. (e.g.DBNE Y, rel)

2.1.4 Stack Pointer

- In the cases of subroutine call, Interrupt and PUSH, POP, RETI, RET instruction,

stack data on RAM or in the case of returning, assign the storage location having

stacked data.

- Stack area is constrained within 1-page (00H-FFH). The SP is post-decremented

when a subroutine call or a push instruction is executed, or when an interrupt is

accepted; and the SP is pre-incremented when a return or a pop instruction is

executed.

- SP should be initialized as follows

ex) LDX #0FEH

: 0FEH ¡æ X reg.

TXSP

: X reg. ¡æ SP

- The behaviors of stack pointer according to each instruction are the following.

GMS81032 Datasheet(PDF) 25 Page - Hynix Semiconductor