TC1796
System Units (Vol. 1 of 2)
Peripheral Control Processor (PCP)
User’s Manual 11-26 V2.0, 2007-07
PCP, V2.0
It is recommended that all EXIT instructions for all channels should use the EP = 0
setting when the PCP is operated in Channel Restart Mode (see Page 11-89).
Note that when Channel Restart Mode is in use a Channel Entry Table must be provided
with a valid entry for every channel being used. Figure 11-10 shows an example of
CMEM organization when Channel Restart Mode has been selected. Failure to provide
a valid entry for all channels that are in use will lead to invalid PCP operation.
11.3.3.2 Channel Resume Mode
Channel Resume Mode is selected with PCP_CS.RCB = 0. In this mode, the user can
arbitrarily determine the address at which the channel program will be started the next
time it is invoked. For this purpose, the PC is saved and restored as part of the context
of a PCP channel.
Additional flexibility is available when Channel Resume Mode is globally selected by
configuring each EXIT instruction to determine the channel start address to be used on
the next invocation of a channel (see Page 11-89). When the EP = 0 setting is used, the
PC value saved in the channel’s context (saved in CPC) is the address of the appropriate
location in the channel entry table. This forces the channel to start at the appropriate
location in the interrupt entry table at next invocation. When the EP = 1 setting is used,
the PC value saved in the channel’s context is the address of the instruction immediately
following the EXIT instruction. The use of the EP = x setting with the EXIT instruction
allows the mixture of channels that use a Channel Restart strategy with others using a
Channel Resume strategy, and also allows individual channels to use either strategy as
appropriate on different invocations.
Note: A valid entry within a Channel Entry Table must be provided for every channel that
uses an EXIT instruction with the EP = 0 setting when Channel Resume Mode has
been selected. Failure to provide a valid entry for such channels will lead to invalid
PCP operation.
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