PXS20RM Datasheet, PDF (419/1368 Pages) Freescale Semiconductor, Inc – PXS20 Microcontroller

Enhanced Direct Memory Access (eDMA)
Table 19-28. TCDn Word 1 (TCDn.{smod,ssize,dmod,dsize,soff}) field descriptions
Name
smod[0:4]
Description
Source address modulo
Value
0 Source address modulo feature is disabled.
ssize[0:2]
dmod[0:4]
dsize[0:2]
soff[16:31]
Source data transfer size
Destination address modulo
Destination data transfer size
Source address signed offset
non-0
The value defines a specific address bit which is
selected to be either the value after saddr + soff
calculation is performed or the original register value.
This feature provides the ability to easily implement a
circular data queue. For data queues requiring
power-of-2 “size” bytes, the queue should be based at
a 0-modulo-size address and the smod field set to the
appropriate value to freeze the upper address bits. The
bit select is defined as ((1 << smod[4:0]) - 1) where a
resulting 1 in a bit location selects the next state
address for the corresponding address bit location and
a 0 selects the original register value for the
corresponding address bit location. For this application,
the soff is typically set to the transfer size to implement
post-increment addressing with the smod function
constraining the addresses to a 0-modulo-size range.
000 8-bit
001 16-bit
010 32-bit
011 64-bit
100 Reserved
101 32-byte burst (64-bit × 4)
110 Reserved
111 Reserved
See the smod[5:0] definition.
See the ssize[2:0] definition.
Sign-extended offset applied to the current source
address to form the next-state value as each source
read is completed.
Figure 19-20 and Table 19-29 define word 2 of the TCDn structure, the nbytes field.
Register address: DMA_Offset + 0x1000 + (32 x n) + 0x08
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
R
nbytes[0:15]
W
RESET: -
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
R
nbytes[16:31]
W
RESET: -
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
= Unimplemented
Figure 19-20. TCDn Word 2 (TCDn.nbytes) Field (DMACR[EMLM] = 0)
Freescale Semiconductor
PXS20 Microcontroller Reference Manual, Rev. 1
19-23