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Enhanced Direct Memory Access (eDMA)
Freescale Semiconductor
19-23
Table 19-30. TCD
n
_CSR Field Descriptions
Field
Description
15–14
BWC
Bandwidth control. Throttles the amount of bus bandwidth consumed by the eDMA. In general, as the
eDMA processes the minor loop, it continuously generates read/write sequences until the minor count is
exhausted. This field forces the eDMA to stall after the completion of each read/write access to control the
bus request bandwidth seen by the crossbar switch (XBS).
00 No eDMA engine stalls
01 Reserved
10 eDMA engine stalls for 4 cycles after each r/w
11 eDMA engine stalls for 8 cycles after each r/w
Note:
If the source and destination sizes are equal, this field is ignored between the first and second
transfers and after the last write of each minor loop. This behavior is a side effect of reducing start-up
latency.
13–12
Reserved, must be cleared.
11–8
MAJOR_LINKCH
Link channel number.
If (MAJOR_E_LINK = 0) then
• No channel-to-channel linking (or chaining) is performed after the major loop counter is exhausted.
else
• After the major loop counter is exhausted, the eDMA engine initiates a channel service request at the
channel defined by these four bits by setting that channel’s TCD
n
_CSR[START] bit.
0–15 Link to DMA channel 0–15
7
DONE
Channel done. This flag indicates the eDMA has completed the major loop. The eDMA engine sets it as the
CITER count reaches zero; The software clears it, or the hardware when the channel is activated.
Note:
This bit must be cleared to write the MAJOR_E_LINK or E_SG bits.
6
ACTIVE
Channel active. This flag signals the channel is currently in execution. It is set when channel service begins,
and the eDMA clears it as the minor loop completes or if any error condition is detected.
5
MAJOR_E_LINK
Enable channel-to-channel linking on major loop complete. As the channel completes the major loop, this
flag enables the linking to another channel, defined by MAJOR_LINKCH. The link target channel initiates
a channel service request via an internal mechanism that sets the TCD
n
_CSR[START] bit of the specified
channel.
Note:
To support the dynamic linking coherency model, this field is forced to zero when written to while the
TCD
n
_CSR[DONE] bit is set.
0 The channel-to-channel linking is disabled.
1 The channel-to-channel linking is enabled.
4
E_SG
Enable scatter/gather processing. As the channel completes the major loop, this flag enables scatter/gather
processing in the current channel. If enabled, the eDMA engine uses DLAST_SGA as a memory pointer to
a 0-modulo-32 address containing a 32-byte data structure loaded as the transfer control descriptor into the
local memory.
Note:
To support the dynamic scatter/gather coherency model, this field is forced to zero when written to
while the TCD
n
_CSR[DONE] bit is set.
0 The current channel’s TCD is normal format.
1 The current channel’s TCD specifies a scatter gather format. The DLAST_SGA field provides a memory
pointer to the next TCD to be loaded into this channel after the major loop completes its execution.
3
D_REQ
Disable request. If this flag is set, the eDMA hardware automatically clears the corresponding EDMA_ERQ
bit when the current major iteration count reaches zero.
0 The channel’s EDMA_ERQ bit is not affected.
1 The channel’s EDMA_ERQ bit is cleared when the major loop is complete.
Summary of Contents for MCF54455
Page 33: ...xxviii Freescale Semiconductor ...
Page 67: ...Freescale Semiconductor 1 ...
Page 125: ...Freescale Semiconductor 1 ...
Page 145: ...Enhanced Multiply Accumulate Unit EMAC 5 21 Freescale Semiconductor ...
Page 173: ...Cache 6 28 Freescale Semiconductor ...
Page 179: ...Static RAM SRAM 7 6 Freescale Semiconductor ...
Page 207: ...Power Management 9 16 Freescale Semiconductor ...
Page 323: ...Reset Controller Module 13 8 Freescale Semiconductor ...
Page 389: ...Pin Multiplexing and Control 16 44 Freescale Semiconductor ...
Page 575: ...PCI Bus Controller 22 58 Freescale Semiconductor ...
Page 600: ...Advanced Technology Attachment ATA Freescale Semiconductor 23 25 ...
Page 601: ...Freescale Semiconductor 1 ...
Page 842: ...I2 C Interface Freescale Semiconductor 33 16 ...
Page 843: ...Freescale Semiconductor 1 ...
Page 921: ...Revision History A 6 Freescale Semiconductor ...