XC2200 Derivatives
System Units (Vol. 1 of 2)
Interrupt and Trap Functions
User’s Manual
5-27
V2.1, 2008-08
ICU_X2K, V2.2
The PEC transfer counter allows service of a specified number of requests by the
respective PEC channel, and then (when COUNT reaches 00
H
) activation of an interrupt
service routine, either associated with the PEC channel’s priority level or with the general
end-of-PEC interrupt. After each PEC transfer, the COUNT field is decremented (except
for COUNT = FF
H
) and the request flag is cleared to indicate that the request has been
serviced.
When COUNT contains the value 00
H
, the respective PEC channel remains idle and the
associated interrupt service routine is activated instead. This allows servicing requests
on all priority levels by standard interrupt service routines.
Continuous transfers
are selected by the value FF
H
in bitfield COUNT. In this case,
COUNT is not modified and the respective PEC channel services any request until it is
disabled again.
When COUNT is decremented from 01
H
to 00
H
after a transfer, a standard interrupt is
requested which can then handle the end of the PEC block transfer (channel-specific
interrupt or common end-of-PEC interrupt, see
).
