DMA Programming Model
MSC8144E Reference Manual, Rev. 3
Freescale Semiconductor
14-45
NPRT
28
Next Port
When size reaches zero and CONT is set, DMACHCR[SPRT]
(for source buffers) or DMACHCR[DPRT] (for destination
buffers) is updated according to the NPRT field:
0 Next buffer port is MBus port 0.
1 Next buffer port is MBus port 1.
NO_INC
27
Increment Address
Indicates the behavior of the buffer address after the request
is serviced.
Note:
When this bit is set, the DMA controller always
issues requests for the same address. It aligns (to
the transfer size) on the first transfer as it does for
any other first transaction. The DMA controller
handles BD_SIZE as if it were a normal buffer, that
is, it issues requests with the total byte count size as
recorded in the BD_SIZE field.
0 Increment
address.
1 Do not increment address.
—
26
Reserved. Write to zero for future compatibility.
NBD
25–16
Next Buffer
When size reaches zero and CONT is set, the next request
calls the buffer to which NBD points.
CNT
15–14
Channel Counter
This field is valid only when the arbitration is time-based. It
characterizes the time-based arbitration mechanism for
continuous buffers when the buffer size reaches zero and
applies only when switching buffers.
00
Continuous: Channel and counter
continue working normally.
01 Reserved.
10 Reserved.
11
Resets the channel counter.
PP
13–12
Port priority
Define priority for this buffer. The bus Interface will set priority
for this buffer. Note that the user must map the priority in
system level.
00
Priority 0 (lowest).
11
Priority 3 (highest).
TSZ
11–8
Transfer size
Indicates the maximum transfer size that the DMA will issue
when request is detected.
0000 512
bytes
0001 1
byte.
0010 2
bytes.
0011 4
bytes.
0100 8
bytes.
0101 16
bytes.
0110 32
bytes.
0111 64
bytes.
1000 128
bytes.
1001 256
bytes.
1010 512
bytes.
1011 1024
bytes.
11xx Reserved.
—
7
Reserved. Write to zero for future compatibility.
FRZ
6
Freeze channel
When size reaches zero, the channel can be frozen. The
already serviced requests continue normally. No further
requests are issued for the associated channel until the host
defrosts it.
0 Normal
operation
1 Freeze
channel.
Table 14-29. BD_ATTR Field Descriptions (Continued)
Bits
Description
Settings
Содержание MSC8144E
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