MPC563XM Reference Manual, Rev. 1
796
Freescale Semiconductor
Preliminary—Subject to Change Without Notice
23.4.4.3
Coherent Dual-parameter Controller - CDC
Dual-parameter coherency is supported by a Coherent Dual-parameter Controller hardware - CDC, which
contends with microengine for SPRAM access. CDC atomically transfers, upon Host’s command, two
parameters from one area of the SPRAM to another. One area is a temporary (buffer) area, where the two
parameters are directly read or written by the Host. This temporary area has to begin in an SPRAM address
multiple of 2 words, and the two parameters must be sequential. The other area is the channel parameter
area where the microcode normally accesses the parameters, usually with the channel relative address
mode (see
Section 23.4.9.1.1, “SPRAM Addressing Modes
). In this area, the parameters transferred by
CDC don’t have to be sequential. A transfer from the temporary area to the channel area, when the Host
sends data to the channel, is called a
write transfer
. Inversely, in a
read transfer
the parameters are
copied from the channel area to the temporary area (channel to Host).
Coherency is guaranteed by the SPRAM access contention rules implemented in the SPRAM arbiter (see
Section 23.4.4.5, “SPRAM Arbitration
”). CDC transfers are coherent in respect to the two Engines, so the
target parameters in the channel area may be shared by channels on them both. During CDC operation, the
Host may suffer from 3 up to 11 system clocks wait states
1
, and the Microengine(s) may suffer up to 2
microcycle wait-states
2
. CDC accesses are atomic with respect to Microengine(s) accesses to the SPRAM.
Even when neither engine is in TST, CDC may suffer up to 4 system clock internal wait-states from
SPRAM arbiter, meaning 9 Skyblue wait-states to Host, so that it does not break atomic back-to-back
accesses from microengine(s). CDC also cannot break TST preload accesses. Host can initiate CDC
back-to-back transfers: there is no need of idle Skyblue cycles between two transfers.
23.4.4.3.1
CDC Programming
The Coherent Dual-parameter Controller Register (see
Section 23.3.2.2, “ETPUCDCR - eTPU Coherent
Dual-Parameter Controller Register
) is used to configure and initiate CDC transfers between the
temporary area and channel parameter area. Host asserts STS bit in order to start the data transfer. CDC
then contends for the SPRAM and starts the transfer. When the data transfer is complete, STS returns to
0. Host receives wait-states for writing STS=1 while CDC contends for SPRAM and during the transfer.
The write access ends when CDC finishes the transfer. Host receives wait-states during the CDC transfer.
If Host writes ETPUCDCR with STS=0 or does not write the STS byte, the CDC transfer does not occur.
CDC programming can be summarized as follows:
1. if it is a write transfer, i.e., from Host to channel, write the two parameters into temporary area.
2. write ETPUCDCR with STS=1 and the remaining CDC programming parameters: parameter
width (32 or 24 bits, field PWIDTH), transfer direction (read or write, field WR), temporary
parameter area base address (field PBBASE), and the absolute addresses of the parameters to be
transferred (concatenation of the fields CTBASE and PARM0/1).
3. if it is a read transfer, i.e., from channel to host, read the two parameters from the temporary area
into Host memory/registers.
1.
The maximum number of Host wait states on CDC occurs when both microengines overlap their TSTs, delayed 3 system
clocks from each other.
2.
One microcycle takes two system clocks. Microengines get wait-states in multiples of microcycles, while Host and CDC
wait-states are multiples of system clocks.
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