s3c72m9 Samsung Semiconductor, Inc., s3c72m9 Datasheet - Page 28

• Manufacturer Part Number: s3c72m9
• Description: The S3c72m5/s3c72m7/s3c72m9 Single-chip Cmos Microcontroller Has Been Designed For High Performance Using Samsung S
• Manufacturer: Samsung Semiconductor, Inc.

ADDRESS SPACES
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.
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.
2-12
Figure 2-6. 1-Bit, 4-Bit, and 8-Bit Accumulator
EA
A
C
1-Bit Accumulator
4-Bit Accumulator
8-Bit Accumulator
S3C72M5/C72M7/C72M9/P72M9 (Preliminary Spec)