Z86E3016PSG Datasheet, PDF (173/348 Pages) Zilog, Inc. – Z86E3016PSG

Z8 CPU
User Manual
155
the service routine. The service routine services the request, resets its
Request Bit in the IRQ, and branches or returns back to the main pro-
gram. An example of a polling routine is as follows:
TM IRQ, #MASKA
JR Z, NEXT
CALL SERVICE
NEXT:
.
.
.
SERVICE:
.
.
.
AND IRQ, #MASKB
RET
;Test for request
;If no request go to NEXT
;If request is there, then
;service it
;Process Request
;Clear Request Bit
;Return to next
In this example, if IRQ2 is being polled, MASKA will be 00000100b
and MASKB will be 11111011b.
Reset Conditions
Upon reset, all bits in IPR are undefined.
In IMR, bit 7 is 0 and bits 0–6 are undefined. The IRQ register is reset and
held in that state until an enable interrupt (EI) instruction is executed.
UM001602-0904
Interrupts