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
C
C =1
NOV
OV = 0
OV
OV = 1
BIO
BIO low
NTC
TC = 0
TC
TC = 1
UNC
Unconditionally
‡
Opcode
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
ZLVC
ZLVC
TP
1
1
0
1
1
1
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