Yamaha YMF724F specifications DMA Emulation Protocol, Pc/Pci

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

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-1 supports only 8-bit DMA channels (DMA Channel 0-3). It also only supports Single DMA transfer.

September 21, 1998

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