ZiLOG Z8 Technical Manual

To initiate polled processing, check the bits of
interest in the IRQ using the Test Under Mask (1M)
instruction. If the bit is set, call or branch to
the service routine. The service routine services
the request, resets its Request bit in the IRQ,
and branches or returns back to the main program.
An example of a polling routine is as follows:
TM IRQ,IIMASK
JR Z NEXT
CALL SERVICE
NEXT:
!Test for request
!If no request go to NEXT
!If request is there
!then service it
SERVICE: ! Process Request
AND IRQ,IIMASK_ !Clear Request bit
RET !Return to next
In this example, if IRQ2 is being polled, MASK
will be ~~200000100 (in binary) and MASK_ will be
%211111011.
Interrupts
10.8 RESET CONDITIONS
During a reset, all bits in IPR are undefined.
In IMR, bit 07 is 0 and bits DO-OS are undefined.
Bit 06 is not implemented, though reading this bit
returns O.
IRQ bits DO-OS are held at 0 until an EI instruc-
tion is eX,ecuted. Bits D6 and D7 are not imple-
mented, but reading
these bits returns O.
10-7

ZiLOG Z8 Specifications

General

Brand	ZiLOG
Model	Z8
Category	Desktop
Language	English