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CS4281 Programming Manual
DS308PRM1
101
Confidential Draft
3/7/00
11.5.5
DMA Mode Register n (DMRn)
Address:
BA0: 150h, Read-Write, for DMA Engine 0
BA0: 158h, Read-Write, for DMA Engine 1
BA0: 160h, Read-Write, for DMA Engine 2
BA0: 168h, Read-Write, for DMA Engine 3
Default:
00000000h
Definition: Core powered. This register hold the mode and format conversion bit fields for the DMA engine.
This register also controls the format for the FIFO block in Polled mode. The DMAn engine is
enabled whenever either
POLL
or
DMA
is enabled. If
DMA
=
POLL
= 0, this DMA engine is idle
and moves no data. The lower byte corresponds to the 8237 mode register. The upper word
controls the data format conversion performed by the engine. See the Data Format Conversion
section for details of data conversions.
Bit Descriptions:
DMA
When set, DMAn is enabled in DMA mode.
DMA
and
POLL
are mutually exclusive. When
DMA
goes from a 0 to a 1, the DMA engine is placed in an initial state with
HDSRn.CH1P
and
HDSRn.CH2P
in their initial state. After
DMA
is set,
DCRn.MSK
is used to control DMAn
starting and stopping.
POLL
When set, DMAn is enabled and in polled I/O mode.
DMA
and
POLL
are mutually exclusive.
When
POLL
is set, DMAn manages the transfer of data between the PCI bus (Host) and
FIFOn.
POLL
transferring from 0 to 1 forces the
HDSRn.CH1P
and
HDSRn.CH2P
bits to their
initial state and initializes the DMAn controller for polled operation.
TBC
Transfer By Channel. When set, this bit forces stereo data to be transferred one channel at a
time across the PCI bus for 8- and 16-bit data formats. When clear, the DMA controller
decides whether to transfer stereo data as a sample or one channel at a time, based on the Base
Address (DBAn) lower two address bits and the sample size (
SIZE8
).
CBC
Count By Channel. When clear, the DMA Count Register, DCCn, counts by sample:
decrements once per sample in mono or stereo (2 channel) format. When
CBC
is set, DCCn
counts by channel: decrements once per sample in mono format, twice per sample in stereo
format (once for left channel, once for right channel). Note that this bit is autonomous to the
DMA’s ability to transfers channels or samples across the PCI bus (which is controlled through
data format and Base addresses).
The following bits:
SIZE20
,
USIGN
,
BEND
,
MONO
, and
SIZE8
define the host memory data format for
DMA and Polled FIFO mode. They have no effect on host reads and writes directly into FIFO
memory.
SWAPC
Swap channels. Swaps the two channels interfacing with the PCI bus.
SIZE20
Sample is 20-bit (4 bytes) audio data. This bit and
SIZE8
cannot both be active. For host-to-
FIFO transfers, the 20 most significant bits of a 32-bit dword are stored. For FIFO-to-host
transfers, the data is MSB-aligned in a 32-bit dword, with the unused lower 12 bits set to 0.
USIGN
Sample is unsigned. When set, the MSB will be inverted since the internal format must be
signed.
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
DMA
POLL
TBC
CBC
SWAPC
SIZE20
USIGN
BEND
MONO
SIZE8
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
TYPE1
TYPE0
DEC
AUTO
TR1
TR0
D
ra
ft
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