YMF724F
3. DMA Emulation Protocol
The former synthesizer LSI for the ISA bus such as the Sound Blaster used the DMA controller (8237: ISA
DMAC) on the system to transfer the sound data from/to the host.
For DS-1, however, ISA DMAC must be used to transfer the sound data to the Sound Blaster Pro Block of
the Legacy Audio Block.
Because signals to connect to the ISA DMAC are generally not available on the PCI bus, there are two ways
proposed from the industry to emulate the ISA DMAC on the PCI bus. One is PC/PCI and the other is D-
DMA.
DS-1 supports both protocols for transferring SB Pro sound data on the PCI bus.
3-1. PC/PCI
DS-1 provides two signals, PCREQ# and PCGNT# to realize the PC/PCI. The format of the signals is
shown below. DS-1 asserts PCREQ# and sets PCREQ# to “HIGH” using the PCICLK corresponding to the
DMA channel it is going to use.
In addition, DS-1 determines whether the next PCI I/O cycle is its own from the channel information that is
encoded in PCGNT#.
0ns
100ns
200ns
300ns
400ns
PCICLK
REQ#
start
CH0 CH1 CH2 CH3
CH4 CH5
CH6 CH7
GNT#
start
bit0
bit1 bit2
PCGNT# is encoded as follows.
GNT# Encoding
GNT# Bits
bit2
bit1
bit0
DMA Channel 0
DMA Channel 1
DMA Channel 2
DMA Channel 3
Reserved
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
DMA Channel 5
DMA Channel 6
DMA Channel 7
DS-1 supports only 8-bit DMA channels (DMA Channel 0-3). It also only supports Single DMA transfer.
January 14, 1999
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YAMAHA [ YAMAHA CORPORATION ]
