MPC563XM Reference Manual, Rev. 1
146
Freescale Semiconductor
Preliminary—Subject to Change Without Notice
Table 7-24. TCDn Word 5 (TCDn.{doff,citer}) Field Descriptions
Name
Description
Value
citer.e_link
Enable channel-to-channel linking
on minor loop complete
As the channel completes the inner minor loop, this
flag enables the linking to another channel, defined
by citer.linkch[5:0]. The link target channel initiates a
channel service request via an internal mechanism
that sets the TCD.start bit of the specified channel. If
channel linking is disabled, the citer value is extended
to 15 bits in place of a link channel number. If the
"major" loop is exhausted, this link mechanism is
suppressed in favor of the major.e_link channel
linking.
This bit must be equal to the biter.e_link bit
otherwise a configuration error will be reported.
0 The channel-to-channel linking is disabled.
1 The channel-to-channel linking is enabled.
citer[14:9]
or
citer.linkch[5:0]
Current “major” iteration count
or
Link channel number
if (TCD.citer.e_link = 0) then
No channel-to-channel linking (or chaining) is
performed after the inner "minor" loop is exhausted.
TCD word 5, bits [30:25] are used to form a 15 bit citer
field.
else
After the "minor" loop is exhausted, the dma_engine
initiates a channel service request at the channel
defined by citer.linkch[5:0] by setting that channel’s
TCD.start bit.
The value contained in citer.linkch[5:0] must not
exceed the number of implemented channels.
citer[8:0]
Current “major” iteration count
This 9 or 15-bit count represents the current major
loop count for the channel. It is decremented each
time the minor loop is completed and updated in the
transfer control descriptor memory. Once the major
iteration count is exhausted, the channel performs a
number of operations (e.g., final source and
destination address calculations), optionally
generating an interrupt to signal channel completion
before reloading the citer field from the beginning
iteration count (biter) field.
When the citer field is initially loaded by software, it
must be set to the same value as that contained in the
biter field.
If the channel is configured to execute a single
service request, the initial values of biter and citer
should be 0x0001.
doff[15:0]
Destination address signed offset
Sign-extended offset applied to the current
destination address to form the next-state value as
each destination write is completed.