Enhanced Direct Memory Access (eDMA)
MPC5510 Microcontroller Family Reference Manual, Rev. 1
12-22
Freescale Semiconductor
Preliminary
161–166 /
0x14 [1:6]
CITER
[0:5]
or
CITER.LINKCH
[0:5]
Current major iteration count or link channel number.
If channel-to-channel linking is disabled (TCD.CITER.E_LINK = 0), then
• No channel-to-channel linking (or chaining) is performed after the inner minor loop is
exhausted. TCD bits [161:175] are used to form a 15-bit CITER field.
Otherwise,
• After the minor loop is exhausted, the DMA engine initiates a channel service request
at the channel defined by CITER.LINKCH[0:5] by setting that channel’s TCD.START
bit.
167–175 /
0x14 [7:15]
CITER
[6:14]
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. After the major iteration count is
exhausted, the channel performs a number of operations (for example, 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.
Note: When the CITER field is initially loaded by software, it must be set to the same
value as that contained in the BITER field.
Note: If the channel is configured to execute a single service request, the initial values
of BITER and CITER should be 0x0001.
176–191 /
0x14 [16:31]
DOFF
[0:15]
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.
192–223 /
0x18 [0:31]
DLAST_SGA
[0:31]
Last destination address adjustment or the memory address for the next transfer control
descriptor to be loaded into this channel (scatter-gather).
If scatter-gather processing for the channel is disabled (TCD.E_SG = 0) then
• Adjustment value added to the destination address at the completion of the outer major
iteration count.
This value can be applied to restore the destination address to the initial value, or adjust
the address to reference the next data structure.
Otherwise,
• This address points to the beginning of a 0-modulo-32 byte region containing the next
transfer control descriptor to be loaded into this channel. This channel reload is
performed as the major iteration count completes. The scatter-gather address must be
0-modulo-32 byte, otherwise a configuration error is reported.
224 /
0x1C [0]
BITER.E_LINK
Enables 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
BITER.LINKCH[0:5]. 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 BITER 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.
0 The channel-to-channel linking is disabled.
1 The channel-to-channel linking is enabled.
Note: When the TCD is first loaded by software, this field must be set equal to the
corresponding CITER field, otherwise a configuration error will be reported. As the major
iteration count is exhausted, the contents of this field is reloaded into the CITER field.
Table 12-19. TCDn Field Descriptions (continued)
Bits /
Word Offset
[n:n]
Name
Description
