Zilog Z80380 Manual do Utilizador descarregar pdf (Página 106)

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Z380

™

USER'S MANUAL

DC-8297-03

ZILOG

IND

INPUT AND DECREMENT (BYTE)

IND

Operation: (HL) ← (C)

B ← B – 1

HL ← HL – 1

This instruction is used for block input of strings of data. During the I/O transaction the 32-

bit BC register is placed on the address bus. Note that the B register contains the loop count

for this instruction so that A15-A8 are not useable as part of a fixed port address.

First the byte of data from the selected peripheral is loaded into the memory location

addressed by the HL register. Then the B register, used as a counter, is decremented by

one. The HL register is then decremented by one, thus moving the pointer to the next

destination for the input.

Flags: S: Unaffected

Z: Set if the result of decrementing B is zero; cleared otherwise

H: Unaffected

V: Unaffected

N: Set

C: Unaffected

Addressing Execute

Mode Syntax Instruction Format Time Note

IND 11101101 10101010 2+i+w

1 2 ... 101 102 103 104 105 106 107 108 109 110 111 ... 267 268

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