PXS20RM Datasheet, PDF (401/1368 Pages) Freescale Semiconductor, Inc – PXS20 Microcontroller

Enhanced Direct Memory Access (eDMA)
and the major loop address offsets (slast and dlast_sga) are used to compute the next saddr and daddr
values.
When minor loop mapping is enabled (DMACR[EMLM] = 1), TCDn word2 is redefined. A portion of
TCDn word2 is used to specify multiple fields: an source enable bit (smloe) to specify the minor loop offset
should be applied to the source address (saddr) upon minor loop completion, an destination enable bit
(dmloe) to specify the minor loop offset should be applied to the destination address (daddr) upon minor
loop completion, and the sign extended minor loop offset value (mloff). The same offset value (mloff) is
used for both source and destination minor loop offsets. When either minor loop offset is enabled (smloe
set or dmloe set), the nbytes field is reduced to 10 bits. When both minor loop offsets are disabled (smloe
cleared and dmloe cleared), the nbytes field is a 30-bit vector.
When minor loop mapping is disabled (DMACR[EMLM] = 0), all 32 bits of TCDn word2 are assigned to
the nbytes field. See Section 19.2.1.17, Transfer Control Descriptor (TCD), for more details.
See Figure 19-2 and Table 19-2 for the DMACR definition.
Register address: DMA_Offset + 0x0000
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
R
0 0 0 0 0 0 0 0 0 0 0 0 0 0 CX ECX
W
RESET: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
R
0 0 0 0 0 0 0 0 EML CLM HALT HOE 0 ERC EDB EBW
W
M
AG
RESET: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
= Unimplemented
Figure 19-2. eDMA Control Register (DMACR)
Name
CX
Table 19-2. eDMA Control Register (DMACR) field descriptions
Description
Cancel Transfer
Value
0 Normal operation.
1 Cancel the remaining data transfer. Stop the
executing channel and force the minor loop to be
finished. The cancel takes effect after the last write
of the current read/write sequence. The CXFR bit
clears itself after the cancel has been honored. This
cancel retires the channel normally as if the minor
loop was completed.
Freescale Semiconductor
PXS20 Microcontroller Reference Manual, Rev. 1
19-5