Zilog Z80380 Manual de usuario descargar pdf (Pagina 153)

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Z380

™

USER'S MANUAL

ZILOG

DC-8297-03

OTIR

OUTPUT, INCREMENT AND REPEAT (BYTE)

OTIR

Operation: repeat until (B=0) begin

B ← B – 1

HL ← HL + 1

end

This instruction is used for block output of strings of data. The string of output data is loaded

into the selected peripheral from memory at consecutive addresses, starting with the

location addressed by the HL register and increasing. 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 A(15-8) 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 incremented by one, thus moving the pointer to the next source for the

output. If the result of decrementing the B register is 0, the instruction is terminated,

otherwise the sequence is repeated. If the B register contains 0 at the start of the execution

of this instruction, 256 bytes are output.

This instruction can be interrupted after each execution of the basic operation. The Program

Counter value at the start of this instruction is saved before the interrupt request is accepted,

so that the instruction can be properly resumed.

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

OTIR 11101101 10110011 2+r+o

1 2 ... 148 149 150 151 152 153 154 155 156 157 158 ... 267 268

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Zilog Z80380 Manual de usuario Pagina 153