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MPC563XM Reference Manual, Rev. 1
162
Freescale Semiconductor
Preliminary—Subject to Change Without Notice
TCD.slast =
-16
TCD.daddr =
0x2000
TCD.doff
= 4
TCD.dsize =
2
TCD.dlast_sga= -16
TCD.int_maj =
1
TCD.start
= 1 (TCD.word7 should be written last after all other fields have been initialized)
All other TCD fields = 0
This would generate the following sequence of events:
1. IPS write to the TCD.start bit requests channel service
2. The channel is selected by arbitration for servicing
3. dma_engine writes: TCD.done = 0, TCD.start = 0, TCD.active = 1
4. dma_engine reads: channel TCD data from local memory to internal register file
5. The source to destination transfers are executed as follows:
a.
read_byte(0x1000), read_byte(0x1001), read_byte(0x1002), read_byte(0x1003)
b.
write_word(0x2000) ->
first iteration of the minor loop
c.
read_byte(0x1004), read_byte(0x1005), read_byte(0x1006), read_byte(0x1007)
d.
write_word(0x2004) ->
second iteration of the minor loop
e.
read_byte(0x1008), read_byte(0x1009), read_byte(0x100a), read_byte(0x100b)
f.
write_word(0x2008) ->
third iteration of the minor loop
g.
read_byte(0x100c), read_byte(0x100d), read_byte(0x100e), read_byte(0x100f)
h.
write_word(0x200c) ->
last iteration of the minor loop
->
major loop complete
6. dma_engine writes: TCD.saddr = 0x1000, TCD.daddr = 0x2000, TCD.citer = 1 (TCD.biter)
7. dma_engine writes: TCD.active = 0, TCD.done = 1, DMAINT[n] = 1
8. The channel retires
The DMAgoes idle or services next channel.
7.5.4.2
Multiple requests
The next example is the same as previous with the exception of transferring 32 bytes via two hardware
requests. The only fields that change are the major loop iteration count and the final address offsets. The
DMAis programmed for two iterations of the major loop transferring 16 bytes per iteration. After the
channel’s hardware requests is enabled in the DMAERQ register, channel service requests are initiated by
the slave device.