MPC5553/MPC5554 Microcontroller Reference Manual, Rev. 5
Freescale Semiconductor 9-23
9.3.1.16 Transfer Control Descriptor (TCD)
Each channel requires a 256-bit transfer control descriptor for defining the desired data movement
operation. The channel descriptors are stored in the local memory in sequential order: channel 0, channel
1,... channel 63 (MPC5554) or channel 0, channel 1,... channel 31 (MPC5553). The definitions of the TCD
are presented as twenty-three variable-length fields. Table 9-17 is field list of the basic TCD structure.
01234567
R ECP 0 GRPPRI CHPRI
W
Reset 0 0 —
1
Reg Addr Base + 0x100 + n
1
The reset value for the group and channel priority fields,
GRPPRI[0–1] and CHPRI[0–3], is equal to the
corresponding channel number for each priority register;
that is, EDMA_CPR31[GRPPRI] = 0b01 and
EDMA_CPR31[CHPRI] = 0b1111.
Figure 9-20. eDMA Channel n Priority Register (EDMA_CPRn)
Table 9-16. EDMA_CPRn Field Descriptions
Bits Name Description
0 ECP Enable channel preemption.
0 Channel n cannot be suspended by a higher priority channel’s service request.
1 Channel n can be temporarily suspended by the service request of a higher priority
channel.
1 — Reserved.
2–3 GRPPRI
[0:1]
Channel n current group priority. Group priority assigned to this channel group when
fixed-priority arbitration is enabled. These two bits are read only; writes are ignored. The
reset value for the group priority fields, is equal to the corresponding channel number for
each priority register; that is, EDMA_CPR31[GRPPRI] = 0b01.
4–7 CHPRI
[0:3]
Channel n arbitration priority. Channel priority when fixed-priority arbitration is enabled.
The reset value for the channel priority fields CHPRI[0–3], is equal to the corresponding
channel number for each priority register; that is, EDMA_CPR31[CHPRI] = 0b1111.
Table 9-17. TCDn 32-bit Memory Structure
eDMA Bit Offset
Lengt
h
TCDn Field Name TCDn Abbreviation
0x1000 + (32 x n) + 0 32 Source Address SADDR
0x1000 + (32 x n) + 32 5 Source address modulo SMOD
0x1000 + (32 x n) + 37 3 Source data transfer size SSIZE
0x1000 + (32 x n) + 40 5 Destination address modulo DMOD
0x1000 + (32 x n) + 45 3 Destination data transfer size DSIZE
0x1000 + (32 x n) + 48 16 Signed Source Address Offset SOFF
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