PXD10RM Datasheet, PDF (499/1332 Pages) Freescale Semiconductor, Inc – PXD10 Microcontroller

Table 15-21. 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]
Source data transfer size
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 16-byte (32-bit AHB bus, WRAP4 burst)
100 reserved (64-bit AHB bus, reserved)
101 32-byte (if supported by the platform)
110 Reserved
111 Reserved
dmod[0:4]
dsize[0:2]
soff[16:31]
Destination address modulo
Destination data transfer size
Source address signed offset
The attempted specification of a 64-bit source size in a
32-bit AMBA AHB bus implementation produces a
configuration error. Likewise, the attempted
specification of a 16-byte source size in a 64-bit AMBA
AHB bus implementation generates a configuration
error. The attempted specification of a 32-byte burst on
platforms that do not support such a transfer type will
result in a configuration error.
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 15-21 and Table 15-22 define word 2 of the TCDn structure, the nbytes field.
Freescale Semiconductor
PXD10 Microcontroller Reference Manual, Rev. 1
Preliminary—Subject to Change Without Notice
15-29