Chapter 10 XGATE (S12XGATEV3)
MC9S12XE-Family Reference Manual , Rev. 1.19
Freescale Semiconductor
399
Operation
FirstOne(RS)
⇒
RD;
Searches the first “1” in register RS (from MSB to LSB) and writes the bit position into the destination
register RD. The upper bits of RD are cleared. In case the content of RS is equal to $0000, RD will be
cleared and the carry flag will be set. This is used to distinguish a “1” in position 0 versus no “1” in the
whole RS register at all.
CCR Effects
Code and CPU Cycles
BFFO
Bit Field Find First One
BFFO
N
Z
V
C
0
∆
0
∆
N:
0; cleared.
Z:
Set if the result is $0000; cleared otherwise.
V:
0; cleared.
C:
Set if RS = $0000
(1)
; cleared otherwise.
1. Before executing the instruction
Source Form
Address
Mode
Machine Code
Cycles
BFFO RD, RS
DYA
0
0
0
0
1
RD
RS
1
0
0
0
0
P
Because
of
an
order
from
the
United
States
International
Trade
Commission,
BGA-packaged
product
lines
and
part
numbers
indicated
here
currently
are
not
available
from
Freescale
for
import
or
sale
in
the
United
States
prior
to
September
2010:
S12XE
products
in
208
MAPBGA
packages