RPTB
Repeat Block
13-210
Example RPTB 127h
Before Instruction After Instruction
PC 0123 PC 0124
RE 0RE 127
RS 0RS 124
ST 0ST 100
LUF 0LUF 0
LV 0LV 0
UF 0UF 0
N0N0
Z0Z0
V0V0
C0C0
Because the block-repeat modes modify the program counter, no
other instruction can modify the program counter at the same time.
The following two rules apply:
Rule 1: The last instruc ti on i n th e bl oc k (o r th e on ly i ns tr uc ti on i n a
block of size 1) cannot be a B
cond
, BR, DB
cond
, CALL,
CALL
cond
, TRAP
cond
, RETI
cond
, RETS
cond
, IDLE, IDLE2,
RPTB, or RPTS. Example 7–3 on page 7-6 shows an
incorrectly placed standard branch.
Rule 2: None of the last four instructions at t he bottom o f the block
(or the only instruction in a block of size 1) can be a
B
cond
D, BRD, or DB
cond
D. Example 7–4 on page 7-7
shows an incorrectly placed delayed branch.
If either rule is violated, the PC will be undefined.