Zilog Z80380 Manual do Utilizador descarregar pdf (Página 161)

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Z380

™

USER'S MANUAL

ZILOG

DC-8297-03

OUTD

OUTPUT AND DECREMENT (BYTE)

OUTD

Operation: B ← B - 1

HL ← HL - 1

This instruction is used for block output 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. The

decremented B register is used in the address.

First the B register, used as a counter, is decremented by one. The byte of data from the

memory location addressed by the HL register is loaded into the selected peripheral. The

HL register is then decremented by one, thus moving the pointer to the next source for the

output.

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

OUTD 11101101 10101011 2+r+o

1 2 ... 156 157 158 159 160 161 162 163 164 165 166 ... 267 268

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