INSTRUCTION SET DESCRIPTIONS
C-40
SHL
SAL
Shift Logical Left:
Shift Arithmetic Left:
SHL
dest, count
SAL
dest, count
Shifts the destination byte or word left
by the number of bits specified in the
count operand. Zeros are shifted in on
the right. If the sign bit retains its
original value, then OF is cleared.
Instruction Operands:
SHL reg, n
SAL reg, n
SHL mem, n
SAL mem, n
SHL reg, CL
SAL reg, CL
SHL mem, CL
SAL mem, CL
(temp)
←
count
do while (temp)
≠
0
(CF)
←
high-order bit of (dest)
(dest)
←
(dest) × 2
(temp)
←
(temp) – 1
if
count = 1
then
if
high-order bit of (dest)
≠
(CE)
then
(OF)
←
1
else
(OF)
←
0
else
(OF) undefined
AF ?
CF
ü
DF –
IF –
OF
ü
PF
ü
SF
ü
TF –
ZF
ü
SAR
Shift Arithmetic Right:
SAR dest, count
Shifts the bits in the destination
operand (byte or word) to the right by
the number of bits specified in the
count operand. Bits equal to the
original high-order (sign) bit are shifted
in on the left, preserving the sign of the
original value. Note that SAR does not
produce the same result as the
dividend of an "equivalent" IDIV
instruction if the destination operand is
negative and 1 bits are shifted out. For
example, shifting –5 right by one bit
yields –3, while integer division –5 by 2
yields –2. The difference in the instruc-
tions is that IDIV truncates all numbers
toward zero, while SAR truncates
positive numbers toward zero and
negative numbers toward negative
infinity.
Instruction Operands:
SAR reg, n
SAR mem, n
SAR reg, CL
SAR mem, CL
(temp)
←
count
do while (temp)
≠
0
(CF)
←
low-order bit of (dest)
(dest)
←
(dest) / 2
(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)
←
0
AF ?
CF
ü
DF –
IF –
OF
ü
PF
ü
SF
ü
TF –
ZF
ü
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
ü
the flag is updated after the instruction is executed
Содержание 80C186XL
Страница 1: ...80C186XL 80C188XL Microprocessor User s Manual...
Страница 2: ...80C186XL 80C188XL Microprocessor User s Manual 1995...
Страница 18: ...1 Introduction...
Страница 19: ......
Страница 27: ......
Страница 28: ...2 Overview of the 80C186 Family Architecture...
Страница 29: ......
Страница 79: ......
Страница 80: ...3 Bus Interface Unit...
Страница 81: ......
Страница 127: ......
Страница 128: ...4 Peripheral Control Block...
Страница 129: ......
Страница 137: ......
Страница 138: ...5 ClockGenerationand Power Management...
Страница 139: ......
Страница 154: ...6 Chip Select Unit...
Страница 155: ......
Страница 178: ...7 Refresh Control Unit...
Страница 179: ......
Страница 193: ......
Страница 194: ...8 Interrupt Control Unit...
Страница 195: ......
Страница 227: ......
Страница 228: ...9 Timer Counter Unit...
Страница 229: ......
Страница 253: ......
Страница 254: ...10 Direct Memory Access Unit...
Страница 255: ......
Страница 283: ......
Страница 284: ...11 Math Coprocessing...
Страница 285: ......
Страница 302: ...12 ONCE Mode...
Страница 303: ......
Страница 306: ...A 80C186 Instruction Set Additions and Extensions...
Страница 307: ......
Страница 318: ...B Input Synchronization...
Страница 319: ......
Страница 322: ...C Instruction Set Descriptions...
Страница 323: ......
Страница 371: ......
Страница 372: ...D Instruction Set Opcodes and Clock Cycles...
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Страница 396: ...Index...
Страница 397: ......