NXP Semiconductors MPC5566, Reference Manual

Page: 370 / 1268

Enhanced Direct Memory Access (eDMA)
MPC5566 Microcontroller Reference Manual, Rev. 2
Freescale Semiconductor 9-9
The eDMA arbitrates channel service requests in four groups (0, 1, 2, 3) of 16 channels each:
• Group 0 contains channels 0–15
• Group 1 contains channels 16–31
• Group 2 contains channels 32-47
• Group 3 contains channels 48-63
Arbitration within a group can be configured to use either fixed-priority or round-robin. In fixed-priority
arbitration, the highest priority channel requesting service is selected to execute. The priorities are
assigned by the channel priority registers. In round-robin arbitration mode, the channel priorities are
ignored and the channels within each group are cycled through, from channel 15 down to channel 0,
without regard to priority.
Refer to Section 9.2.2.16, “eDMA Channel n Priority Registers (EDMA_CPRn) .”
The group priorities operate in a similar fashion. In group fixed-priority arbitration mode, channel service
requests in the highest priority group are executed first where priority level 3 is the highest and priority
level 0 is the lowest. The group priorities are assigned in the GRP
n PRI fields of the eDMA control register
(EDMA_CR). All group priorities must have unique values prior to any channel service requests occur,
otherwise a configuration error is reported. In group round-robin mode, the group priorities are ignored
and the groups are cycled through, from group 3 down to group 0, without regard to priority.
Address: Base + 0x0000 Access: User R/W
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
R 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
W
Reset 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
R
GRP3PRI GRP2PRI GRP1PRI GRP0PRI
0 0 0 0
ERGA ERCA EDBG
0
W
Reset 1 1 1 0 0 1 0 0 0 0 0 0 0 0 0 0
Figure 9-2. eDMA Control Register (EDMA_CR)
Table 9-2. EDMA_CR Field Descriptions
Field Description
0–15 Reserved
16–17
GRP3PRI
Channel group 3 priority. Group 3 priority level when fixed priority group arbitration is enabled.
18–19
GRP2PRI
Channel group 2 priority. Group 2 priority level when fixed priority group arbitration is enabled.
20–21
GRP1PRI
Channel group 1 priority. Group 1 priority level when fixed-priority group arbitration is enabled.