Zilog Z08470 - Manual (Page 304)

Z80 Instruction Set UM008007-0715
292
Z80 CPU
User Manual
IN A, (n)
Operation
A ← (n)
Op Code
IN
Operands
A, (n)
Description
The operand n is placed on the bottom half (A0 through A7) of the address bus to select
the I/O device at one of 256 possible ports. The contents of the Accumulator also appear
on the top half (A8 through A15) of the address bus at this time. Then one byte from the
selected port is placed on the data bus and written to the Accumulator (Register A) in the
CPU.
Condition Bits Affected
None.
Example
The Accumulator contains 23h , and byte 7Bh is available at the peripheral device mapped
to I/O port address 01h . Upon the execution of an IN A, ( 01h ) instruction, the Accumula-
tor contains 7Bh .
M Cycles T States 4 MHz LT.
3 11 (4, 3, 4) 2.75
1 1 1 1 1 0 0 1 DB
n