MPC5553/MPC5554 Microcontroller Reference Manual, Rev. 5
Freescale Semiconductor 9-31
Minor loop TCD variables are soff, smod, doff, dmod, nbytes, saddr, daddr, bwc, active, and
start. Major loop TCD variables are dlast, slast, citer, biter, done, d_req, int_maj, major_lnkch,
and int_half.
For descriptors where the sizes are not equal, multiple access of the smaller size data are
required for each reference of the larger size. As an example, if the source size references 16-bit
data and the destination is 32-bit data, two reads are performed, then one 32-bit write.
• TCD local memory
— Memory controller: This logic implements the required dual-ported controller, handling
accesses from both the eDMA engine as well as references from the slave bus. As noted earlier,
in the event of simultaneous accesses, the eDMA engine is given priority and the slave
transaction is stalled.
— Memory array: The TCD is implemented using a single-ported, synchronous compiled RAM
memory array.
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