Freescale Semiconductor PXR4030, Reference Manual

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Enhanced Direct Memory Access Controller (eDMA)
21-54 Freescale Semiconductor
PXR40 Microcontroller Reference Manual, Rev. 1
2. The channel is selected by arbitration for servicing.
3. eDMA engine writes: EDMA _x _TCD.DONE = 0, EDMA _x _TCD.START = 0,
EDMA _x _TCD.ACTIVE = 1.
4. eDMA 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. eDMA engine writes: EDMA _x _TCD.SADDR = 0x1000, EDMA _x _TCD.DADDR = 0x2000,
EDMA _x _TCD.CITER = 1 (EDMA _x _TCD.BITER).
7. eDMA engine writes: EDMA _x _TCD.ACTIVE = 0, EDMA _x _TCD.DONE = 1,
EDMA _x _IRQR n = 1.
8. The channel retires.
The eDMA goes idle or services the next channel.
21.5.5.2 Multiple Requests
The next example is the same as previous, excepting transferring 32 bytes via two hardware requests. The
only fields that change are the major loop iteration count and the final address offsets. The eDMA is
programmed for two iterations of the major loop transferring 16 bytes per iteration. After the channel’s
hardware requests are enabled in the EDMA_
x _ERQR, channel service requests are initiated by the slave
device (ERQR should be set after TCD). Note that EDMA _x _TCD.START = 0.
EDMA _x _TCD.CITER = EDMA _x _TCD.BITER = 2
EDMA _x _TCD.NBYTES = 16
EDMA _x _TCD.SADDR = 0x1000
EDMA _x _TCD.SOFF = 1
EDMA _x _TCD.SSIZE = 0
EDMA _x _TCD.SLAST = –32
EDMA _x _TCD.DADDR = 0x2000
EDMA _x _TCD.DOFF = 4
EDMA _x _TCD.DSIZE = 2
EDMA _x _TCD.DLAST_SGA = –32
EDMA _x _TCD.INT_MAJ = 1
EDMA _x _TCD.START = 0 (Must be written last after all other fields have been initialized)