Zilog Z08470 Manual do Utilizador descarregar pdf (Página 311)

100

101

UM008007-0715 Z80 Instruction Description

Z80 CPU

User Manual

299

IND

Operation

(HL) ← (C), B ← B – 1, HL ← HL – 1

Op Code

IND

Operands

None.

Description

The contents of Register C are placed on the bottom half (A0 through A7) of the address

bus to select the I/O device at one of 256 possible ports. Register B can be used as a byte

counter, and its contents are placed 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

CPU. The contents of the HL register pair are placed on the address bus and the input byte

is written to the corresponding location of memory. Finally, the byte counter and register

pair HL are decremented.

Condition Bits Affected

S is unknown.

Z is set if B – 1 = 0; otherwise, it is reset.

H is unknown.

P/V is unknown.

N is set.

C is not affected.

M Cycles T States 4 MHz E.T.

4 16 (4, 5, 3, 4) 4.00

11 0 01111

10 0 10011

1 2 ... 306 307 308 309 310 311 312 313 314 315 316 ... 325 326

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Zilog Z08470 Manual do Utilizador Página 311

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