DMA_DCRn field descriptions (continued)
Field
Description
boundary depends on the initial destination address (DAR). The base address should be aligned to a 0-
modulo-(circular buffer size) boundary. Misaligned buffers are not possible. The boundary is forced to the
value determined by the upper address bits in the field selection.
0000
Buffer disabled
0001
Circular buffer size is 16 bytes
0010
Circular buffer size is 32 bytes
0011
Circular buffer size is 64 bytes
0100
Circular buffer size is 128 bytes
0101
Circular buffer size is 256 bytes
0110
Circular buffer size is 512 bytes
0111
Circular buffer size is 1 KB
1000
Circular buffer size is 2 KB
1001
Circular buffer size is 4 KB
1010
Circular buffer size is 8 KB
1011
Circular buffer size is 16 KB
1100
Circular buffer size is 32 KB
1101
Circular buffer size is 64 KB
1110
Circular buffer size is 128 KB
1111
Circular buffer size is 256 KB
7
D_REQ
Disable Request
DMA hardware automatically clears the corresponding DCRn[ERQ] bit when the byte count register
reaches 0.
0
ERQ bit is not affected.
1
ERQ bit is cleared when the BCR is exhausted.
6
Reserved
This field is reserved.
This read-only field is reserved and always has the value 0.
5–4
LINKCC
Link Channel Control
Allows DMA channels to have their transfers linked. The current DMA channel triggers a DMA request to
the linked channels (LCH1 or LCH2) depending on the condition described by the LINKCC bits.
If not in cycle steal mode (DCRn[CS]=0) and LINKCC equals 01 or 10, no link to LCH1 occurs.
If LINKCC equals 01, a link to LCH1 is created after each cycle-steal transfer performed by the current
DMA channel is completed. As the last cycle-steal is performed and the BCR reaches zero, then the link to
LCH1 is closed and a link to LCH2 is created.
00
No channel-to-channel linking
01
Perform a link to channel LCH1 after each cycle-steal transfer followed by a link to LCH2 after the
BCR decrements to 0.
10
Perform a link to channel LCH1 after each cycle-steal transfer
11
Perform a link to channel LCH1 after the BCR decrements to 0.
3–2
LCH1
Link Channel 1
Indicates the DMA channel assigned as link channel 1. The link channel number cannot be the same as
the currently executing channel, and generates a configuration error if this is attempted (DSRn[CE] is set).
00
DMA Channel 0
01
DMA Channel 1
Table continues on the next page...
Memory Map/Register Definition
KL27 Sub-Family Reference Manual , Rev. 5, 01/2016
318
Freescale Semiconductor, Inc.
Содержание MKL27Z128VFM4
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