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INSTRUCTION SET DESCRIPTIONS
C-36
RCL Rotate Through Carry Left:
RCL
dest, count
Rotates the bits in the byte or word
destination operand to the left by the
number of bits specified in the count
operand. The carry flag (CF) is treated
as "part of" the destination operand;
that is, its value is rotated into the low-
order bit of the destination, and itself is
replaced by the high-order bit of the
destination.
Instruction Operands:
RCL reg, n
RCL mem, n
RCL reg, CL
RCL mem, CL
(temp) ← count
do while (temp) ≠ 0
(tmpcf) ← (CF)
(CF) ← high-order bit of (dest)
(dest) ← (dest) × 2 + (tmpcf)
(temp) ← (temp) – 1
if
count = 1
then
if
high-order bit of (dest) ≠ (CF)
then
(OF) ← 1
else
(OF) ← 0
else
(OF) undefined
AF –
CF
DF –
IF –
OF
PF –
SF –
TF –
ZF –
RCR Rotate Through Carry Right:
RCR
dest, count
Operates exactly like RCL except that
the bits are rotated right instead of left.
Instruction Operands:
RCR reg, n
RCR mem, n
RCR reg, CL
RCR mem, CL
(temp) ← count
do while (temp) ≠ 0
(tmpcf) ← (CF)
(CF) ← low-order bit of (dest)
(dest) ← (dest) / 2
high-order bit of (dest) ← (tmpcf)
(temp) ← (temp) – 1
if
count = 1
then
if
high-order bit of (dest) ≠
next-to-high-order bit of (dest)
then
(OF) ← 1
else
(OF) ← 0
else
(OF) undefined
AF –
CF
DF –
IF –
OF
PF –
SF –
TF –
ZF –
Table C-4. Instruction Set (Continued)
Name Description Operation
Flags
Affected
NOTE: The three symbols used in the Flags Affected column are defined as follows:
– the contents of the flag remain unchanged after the instruction is executed
? the contents of the flag is undefined after the instruction is executed
the flag is updated after the instruction is executed