mcf51jf128 Freescale Semiconductor, Inc, mcf51jf128 Datasheet - Page 425

• Manufacturer Part Number: mcf51jf128
• Description: Mcf51jf128 Reference Manual
• Manufacturer: Freescale Semiconductor, Inc

Freescale Semiconductor, Inc.
Reserved
LINKCC
D_REQ
LCH1
Field
5–4
3–2
7
6
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
Disable request
DMA hardware automatically clears the corresponding DCRn[ERQ] bit when the byte count register
reaches zero.
0
1
This read-only bit is reserved and always has the value zero.
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
01
10
11
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
01
10
11
ERQ bit is not affected.
ERQ bit is cleared when the BCR is exhausted.
No channel-to-channel linking
Perform a link to channel LCH1 after each cycle-steal transfer followed by a link to LCH2 after the
BCR decrements to zero
Perform a link to channel LCH1 after each cycle-steal transfer
Perform a link to channel LCH1 after the BCR decrements to zero
DMA Channel 0
DMA Channel 1
DMA Channel 2
DMA Channel 3
Buffer disabled
Circular buffer size is 16 bytes
Circular buffer size is 32 bytes
Circular buffer size is 64 bytes
Circular buffer size is 128 bytes
Circular buffer size is 256 bytes
Circular buffer size is 512 bytes
Circular buffer size is 1 KB
Circular buffer size is 2 KB
Circular buffer size is 4 KB
Circular buffer size is 8 KB
Circular buffer size is 16 KB
Circular buffer size is 32 KB
Circular buffer size is 64 KB
Circular buffer size is 128 KB
Circular buffer size is 256 KB
DMA_DCRn field descriptions (continued)
MCF51JF128 Reference Manual, Rev. 2, 03/2011
Table continues on the next page...
Preliminary
Description
Chapter 19 DMA Controller
425