34
BBC
BBC
B
RANCH ON
B
IT
C
LEAR
When (Mi) or (Ai) = 0, (PC)
←
(PC) + n + REL
(Mi) or (Ai) = 1, (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 M or A and takes
a branch if the bit is 0. The branch address is specified by a
relative address. If the bit is 1, next instruction is executed.
No change
Op e r a t io n :
F u n c t io n :
St a t u s fla g :
Cycle number
4
5
Byte number
2
3
Addressing mode
Accumulator bit
Relative
Zero page bit
Relative
Statement
∆
BBC
∆
i,A,$hhll
∆
BBC
∆
i,$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 BBC instruction after the contents of the interrupt
request bit is changed, one instruction or more must be passed
before the BBC instruction is executed.
Machine codes
(20i+13)
16
, rr
16
(20i+17)
16
,
zz
16
, rr
16
