|
| |
Convert Byte to Word
|
86/88 |
Y |
186 |
Y |
286 |
Y |
386 |
Y |
486 |
Y |
CBW |
|
Ovfl |
N |
Dir |
N |
Int |
N |
Trap |
N |
Sign |
N |
Zero |
N |
Aux |
N |
Prty |
N |
Carry |
N |
CBW extends the sign bit of the AL register into the AH register. This
instruction extends a signed byte value into the equivalent signed
word value.
Note: This instruction will set AH to 0FFh if the sign bit
(bit 7) of AL is set; if bit 7 of AL is not set, AH
will be set to 0. The instruction is useful for
generating a word from a byte prior to performing
byte division.
------------------------------------ Timing ----------------------------------
OpCode Instruction 386 286 86
98 CBW 3 2 2
------------------------------------ Logic -----------------------------------
if (AL < 80h) then
AH = 0
else
AH = FFh
See Also CDQ CWD CWDE DIV IDIV |