YMF740C Datasheet, PDF (34/44 Pages) List of Unclassifed Manufacturers – DS-1L

YMF740C
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-1L, 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 is a way, that
is PC/PCI, proposed from the industry to emulate the ISA DMAC on the PCI bus.
DS-1L supports the protocol for transferring SB Pro sound data on the PCI bus.
3-1. PC/PCI
DS-1L provides two signals, PCREQ# and PCGNT# to realize the PC/PCI. The format of the signals is
shown below. DS-1L asserts PCREQ# and sets PCREQ# to “HIGH” using the PCICLK corresponding to
the DMA channel it is going to use.
In addition, DS-1L 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#
GNT#
start CH0 CH1 CH2 CH3 CH4 CH5 CH6 CH7
start bit0 bit1 bit2
PCGNT# is encoded as follows.
GNT# Encoding
bit2 bit1 bit0 GNT# Bits
0
0
0 DMA Channel 0
0
0
1 DMA Channel 1
0
1
0 DMA Channel 2
0
1
1 DMA Channel 3
1
0
0 Reserved
1
0
1 DMA Channel 5
1
1
0 DMA Channel 6
1
1
1 DMA Channel 7
DS-1L supports only 8-bit DMA channels (DMA Channel 0-3).
It also only supports Single DMA transfer.
January 14, 1999
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