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Return Conditionally
RETC
7-143
Assembly Language Instructions
Syntax RETC
cond
1 [,
cond
2] [
,...
]
Operands
cond Condition
EQ ACC = 0
NEQ ACC ≠ 0
LT ACC < 0
LEQ ACC ≤ 0
GT ACC > 0
GEQ ACC ≥ 0
NC C = 0
CC =1
NOV OV = 0
OV OV = 1
BIO BIO
low
NTC TC = 0
TC TC = 1
UNC Unconditionally
‡
Opcode
0123456789101112131415
ZLVCZLVCTP110111
Note: The TP and ZLVC fields are defined on pages 7-3 and 7-4.
Execution If
cond
1 AND
cond
2 AND ...
(TOS) → PC
Pop stack one level
Else, continue
Status Bits None
Description If the specified condition or conditions are met, a standard return is executed
(see the description for the RET instruction). Note that not all combinations of
conditions are meaningful. For example, testing for LT and GT is contradictory.
In addition, testing BIO
is mutually exclusive to testing TC.
Words 1
Cycles for a Single RETC Instruction
Condition ROM DARAM SARAM External
True 4 4 4 4+4p
False 2 2 2 2+2p
Note: The processor performs speculative fetching by reading two additional instruction
words. If the PC discontinuity is taken, these two instruction words are discarded.
Example RETC GEQ,NOV ;A return is executed if the
;accumulator content is positive
;or zero and if the OV (overflow)
;-bit is zero.
Cycles