35
BBS
BBS
B
RANCH ON
B
IT
S
ET
When (Mi) or (Ai) = 1, (PC)
←
(PC) + n + REL
(Mi) or (Ai) = 0, (PC)
←
(PC) + n
n : If addressing mode is Zero Page Bit Relative, n=3. And if
addressing mode is Accumulator Bit Relative, n=2.
This instruction tests the designated bit i of the M or A and
takes a branch if the bit is 1. The branch address is specified
by a relative address. If the bit is 0, next instruction is exe-
cuted.
No change
Op e r a t io n :
F u n c t io n :
St a t u s fla g :
Machine codes
(20i+3)
16
, rr
16
(20i+7)
16
,
zz
16
, rr
16
Cycle number
4
5
Byte number
2
3
Addressing mode
Accumulator bit
Relative
Zero page bit
Relative
Statement
∆
BBS
∆
i,A,$hhll
∆
BBS
∆
i,$zz,$hhll
Notes 1: rr
16
=$hhll–(
✽
+n). The rr
16
is a value in a range of –128 to +127.
2: When a branch is executed, add 2 to the cycle number.
3: When executing the BBS instruction after the contents of the interrupt
request bit is changed, one instruction or more must be passed
before the BBS instruction is executed.