Z86E3016PSG Datasheet, PDF (271/348 Pages) Zilog, Inc. – Z86E3016PSG

Z8 CPU
User Manual
253
Halt
HALT
Instruction Format
OPC
Cycles
6
OPC
(Hex)
7F
Operation
The HALT instruction turns off the internal CPU clock, but not the XTAL
oscillation. The counter/timers and the external interrupts IRQ1, IRQ2,
and IRQ3 remain active. The devices are recovered by interrupts, either
externally or internally generated.
Flag
C
Z
S
V
D
H
Description
Unaffected
Unaffected
Unaffected
Unaffected
Unaffected
Unaffected
Note: In order to enter HALT mode, it is necessary to first flush the instruction
pipeline to avoid suspending execution in mid-instruction. The user must
execute a NOP immediately before the execution of the HALT instruction.
Example
Assuming the Z8^® CPU is in normal operation, the statements:
NOP
HALT
Op Codes: FF 7F
place the Z8^® CPU into HALT mode.
UM001602-0904
Instruction Description