TC1796
System Units (Vol. 1 of 2)
Peripheral Control Processor (PCP)
User’s Manual 11-24 V2.0, 2007-07
PCP, V2.0
11.3.2.5 Initialization of the Contexts
The programmer is responsible for configuring each channel program’s context before
commencing operation. Because this must be done by writing to the PCP across the FPI
Bus, it is important to understand exactly where each channel program’s context is from
the FPI Bus perspective (see Page 11-48 for details).
11.3.2.6 Context Save Optimization
The PCP has an optimized context-switching strategy consisting of optimization of both
context load and store. During a context load in which the channel that is starting is also
the last channel that the PCP was running then the PCP GPRs already contain the
values appropriate to the channel. In this case there is no need to reload the context (i.e.
the PCP can immediately continue operation at the appropriate point in the code without
having to perform a context load). During a Context Store (i.e. the PCP exits a channel
as a result of EXIT or DEBUG instructions or exits in response to a higher-priority
channel interrupt), only those registers that have been updated (i.e. written to) since the
context was loaded are saved to the CSA.
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