IN | INPUT BYTE OR WORD |
IN
Operation:
(DEST) +- (SRC)
Description:
IN accumulator,port
IN transfers a byte or a word from an input port to the AL register or the AX register, respectively. The port number may be speci- fied either with an immediate byte constant, allowing access to ports numbered 0 through
Flags Affected:
None
255, or with a number previously placed in the DX register, allowing variable access (by changing the value in DX) to ports numbered from 0 through 65,535.
Encoding:
Fixed Port:
1111 001 0 w I port
if vJ = 0 then SRC = port, DEST = AL else SRC = port + 1:port, OEST = AX
Variable Port:
11110110wl
if w = 0 then SRC = (OX), OEST = AL else SRC = (OX) +1:(DX), OEST = AX
IN Operands | Clocks* | Transfers | Bytes | IN Coding Example |
accLimulator, immed8 | 10(14) | 1 | 2 | IN AL,OEAH |
accumulator, DX | 8(12) | 1 | 1 | IN AX, OX |
*b(w): where b denotes the number of clock cycles for byte operands and w denotes the number of clock cycles for word operands.
