Samsung KS57C2308 manual Special-Purpose Working Registers

ADDRESS SPACES KS57C2308/P2308/C2316/P2316

Special-Purpose Working Registers

Register A is used as a 4-bit accumulator and double register EA as an 8-bit accumulator. The carry flag can also be used as a 1-bit accumulator.

8-bit double registers WX, WL and HL are used as data pointers for indirect addressing. When the HL register serves as a data pointer, the instructions LDI, LDD, XCHI, and XCHD can make very efficient use of working registers as program loop counters by letting you transfer a value to the L register and increment or decrement it using a single instruction.

C

A

EA

1-BIT

ACCUMULATOR

4-BIT

ACCUMULATOR

8-BIT

ACCUMULATOR

Figure 2-6. 1-Bit, 4-Bit, and 8-Bit Accumulator

Recommendation for Multiple Interrupt Processing

If more than four interrupts are being processed at one time, you can avoid possible loss of working register data by using the PUSH RR instruction to save register contents to the stack before the service routines are executed in the same register bank. When the routines have executed successfully, you can restore the register contents from the stack to working memory using the POP instruction.

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