Zilog Z08470 - Manual (Page 48)

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7UGT /CPWCN
UM008101-0601 Counter/Timer Channels
Figure 13. Return from Interrupt Cycle
Daisy-Chain Interrupt Servicing
Figure 14 illustrates a typical nested interrupt sequence that may occur in
the CTC. In this example, Channel 2 interrupts and is granted service.
While this channel is being serviced, higher priority Channel 1 interrupts
and is granted service. The service routine for the higher priority channel is
completed, and a RETI instruction is executed to signal the channel that its
routine is complete (see “Return from Interrupt Cycle” on page 29 for
further details). At this time, the service routine of the lower priority
Channel 2 is resumed and completed.
IEO
CLK
INT
IEI
RD
M1
T
1
T
2
T
3
T
4
D
7
–D
0
*INT goes Low if more interrupts are pending on the RTC.
T
1
T
2
T
3
T
4
T
1
ED 4D