TC1796
System Units (Vol. 1 of 2)
Peripheral Control Processor (PCP)
User’s Manual
11-12
V2.0, 2007-07
PCP, V2.0
To distinguish the actual register contents from the copies stored in the PRAM context
regions, the term CRx is used throughout the rest of this document to refer to the register
values in the context regions. Registers R6 and R7 are always handled in a special way
during context save and restore operations, this is described in detail in
The Context Model is selected via a bit field PCP_CS.CS, this is a global setting (i.e. the
selected Context Model is used for all channels). Once a Context Model has been
selected (during PCP configuration) and the PCP has been started the PCP must
continue to use that Context Model. Attempting to change the Context Model in use
during PCP operation will lead to invalid context restore operations which will in turn lead
to invalid PCP operation.
In the case of Small and Minimum Context Models, the unsaved and unrestored
registers (shaded in
) can be thought of as global registers that any channel
program can use or change, or reference as constants – for example as base address
pointers (see
for more detail).
Note: Special care must be taken when using Minimum or Small Context Model with
nested interrupts (see
).