Preliminary
SN8P1702A/SN8P1703A
8-bit micro-controller build-in 12-bit ADC
ACCUMULATOR
The ACC is an 8-bits data register responsible for transferring or manipulating data between ALU and data memory. If
the result of operating is zero (Z) or there is carry (C or DC) occurrence, then these flags will be set to PFLAG register.
ACC is not in data memory (RAM), so ACC can’t be access by “B0MOV” instruction during the instant addressing
mode.
ꢁExample: Read and write ACC value.
; Read ACC data and store in BUF data memory
MOV
.
BUF, A
.
; Write a immediate data into ACC
MOV
.
A, #0FH
.
; Write ACC data from BUF data memory
MOV
.
A, BUF
.
The system doesn’t store ACC and PFLAG value as any interrupt service executed. ACC must be exchanged to
another data memory defined by users. Thus, once interrupt occurs, these data must be stored in the data memory
based on the user’s program as follows.
ꢁExample: ACC and working registers protection.
ACCBUF
EQU
00H
; ACCBUF is ACC data buffer in bank 0.
; B0XCH doesn’t change C, Z flag
INT_SERVICE:
B0XCH
A, ACCBUF
B0XCH
B0MOV
B0MOV
A, ACCBUF
A, PFLAG
PFLAGBUF,A
; Store ACC value
; Store PFLAG value
.
B0MOV
B0MOV
B0XCH
A, PFLAGBUF
PFLAG,A
A, ACCBUF
; Re-load PFLAG value
; Re-load ACC
B0XCH
A, ACCBUF
; Re-load ACC
RETI
; Exit interrupt service vector
ꢀ
Notice: To save and re-load ACC data must be used “B0XCH” instruction, or the PLAGE value maybe
modified by ACC.
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