SAB80515 Datasheet, PDF (146/270 Pages) Siemens Semiconductor Group – 8-Bit Single-Chip Microcontroller Family

Instruction Set
CJNE <dest-byte >, < src-byte >, rel
Function:
Compare and jump if not equal
Description:
CJNE compares the magnitudes of the tirst two operands, and branches if their
values are not equal. The branch destination is computed by adding the signed
relative displacement in the last instruction byte to the PC, after incrementing the
PC to the start of the next instruction. The carry flag is set if the unsigned integer
value of <dest-byte> is less than the unsigned integer value of <src-byte>;
otherwise, the carry is cleared. Neither operand is affected.
The first two operands allow four addressing mode combinations: the accumulator
may be compared with any directly addressed byte or immediate data, and any
indirect RAM location or working register can be compared with an immediate
constant.
Example:
The accumulator contains 34H. Register 7 contains 56H. The first instruction in the
sequence
;
NOT_EQ
;
CJNE
...
JC
...
R7, # 60H, NOT_EQ
.....
REQ_LOW
.....
; R7 = 60H
; If R7 < 60H
; R7 > 60H
sets the carry flag and branches to the instruction at label NOT_EQ. By testing the
carry flag, this instruction determines whether R7 is greater or less than 60H.
If the data being presented to port 1 is also 34H, then the instruction
WAIT: CJNE A,P1,WAIT
clears the carry flag and continues with the next instruction in sequence, since the
accumulator does equal the data read from P1. (If some other value was input on
P1, the program will loop at this point until the P1 data changes to 34H).
Semiconductor Group
146