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SAM47 INSTRUCTION SET KS57C2308/P2308/C2316/P2316
5-26
ADS — Add And Skip On Overflow
ADS dst,src
Operation: Operand Operation Summary Bytes Cycles
A, #im Add 4-bit immediate data to A and skip on overflow 1 1 + S
EA,#imm Add 8-bit immediate data to EA and skip on overflow 2 2 + S
A,@HL Add indirect data memory to A and skip on overflow 1 1 + S
EA,RR Add register pair (RR) contents to EA and skip on
overflow
2 2 + S
RRb,EA Add EA to register pair (RRb) and skip on overflow 2 2 + S
Description: The source operand is added to the destination operand and the sum is stored in the destination.
The contents of the source are unaffected. If there is an overflow from the most significant bit of
the result, the skip signal is generated and a skip is executed, but the carry flag value is
unaffected.
If “ADS A,#im” follows an “ADC A,@HL” instruction in a program, ADC skips the ADS instruction
if an overflow occurs. If there is no overflow, the ADS instruction is executed normally. This skip
condition is valid only for “ADC A,@HL” instructions, however. If an overflow occurs following an
ADS instruction, the next instruction is not skipped.
Operand Binary Code Operation Notation
A, #im 1 0 1 0 d3 d2 d1 d0
A ← A + im; skip on overflow
EA,#imm 1 1 0 0 1 0 0 1
EA ← EA + imm; skip on overflow
d7 d6 d5 d4 d3 d2 d1 d0
A,@HL 0 0 1 1 1 1 1 1
A ← A + (HL); skip on overflow
EA,RR 1 1 0 1 1 1 0 0
EA ← EA + RR; skip on overflow
1 0 0 1 1 r2 r1 0
RRb,EA 1 1 0 1 1 1 0 0
RRb ← RRb + EA; skip on overflow
1 0 0 1 0 r2 r1 0
Examples: 1. The extended accumulator contains the value 0C3H, register pair HL the value 0AAH, and
the carry flag = "0":
ADS EA,HL ; EA ← 0C3H + 0AAH = 6DH
; ADS skips on overflow, but carry flag value is not
affected.
JPS XXX ; This instruction is skipped since ADS had an overflow.
JPS YYY ; Jump to YYY.