YMF754-R datasheet(44/60 Pages) YAMAHA

44 / 60 page

YMF754

June 28, 1999

-44-

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-1E, 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-1E supports both protocols for transferring SB Pro sound data on the PCI bus.

3-1. PC/PCI

DS-1E provides two signals, PCREQ# and PCGNT# to realize the PC/PCI.

The format of the signals is

shown below.

DS-1E asserts PCREQ# and sets PCREQ# to “HIGH” using the PCICLK corresponding to

the DMA channel it is going to use.

In addition, DS-1E determines whether the next PCI I/O cycle is its own from the channel information that is

encoded in PCGNT#.

start

CH0

CH1

CH2

CH3

CH4

CH5

CH6

CH7

start

bit0

bit1

bit2

0ns

100ns

200ns

300ns

400ns

PCICLK

REQ#

GNT#

PCGNT# is encoded as follows.

GNT# Encoding

bit2

bit1

bit0

GNT# Bits

DMA Channel 0

DMA Channel 1

DMA Channel 2

DMA Channel 3

Reserved

DMA Channel 5

DMA Channel 6

DMA Channel 7

DS-1E supports only 8-bit DMA channels (DMA Channel 0-3).

It also only supports Single DMA transfer.

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