YMF744B

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

3-1. PC/PCI

DS-1S provides two signals, PCREQ# and PCGNT# to realize the PC/PCI. The format of the signals is shown below. DS-1S asserts PCREQ# and sets PCREQ# to “HIGH” using the PCICLK corresponding to the DMA channel it is going to use.

In addition, DS-1S 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-1S supports only 8-bit DMA channels (DMA Channel 0-3). It also only supports Single DMA transfer.

February 3, 1999

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Yamaha YMF744B (DS-1S) specifications DMA Emulation Protocol, Pc/Pci

YMF744B (DS-1S) specifications

The Yamaha YMF744B, also known as the DS-1S, is a popular audio chip that emerged in the late 1990s, particularly known for its use in sound cards for PCs. This sound processor exemplifies Yamaha's commitment to delivering high-quality audio through innovative technology and user-friendly features.

One of the standout features of the YMF744B is its ability to support advanced sound synthesis methods, including wave table synthesis and sample playback. These technologies provide users with a rich audio experience, enabling high-fidelity sounds reminiscent of live instruments. The chip is also notable for its ability to emulate MIDI instruments, allowing musicians to create synthesized music that captures the nuances of traditional sounds.

The YMF744B integrates a 16-bit DAC (Digital-to-Analog Converter), which facilitates high-quality audio playback with a sampling rate of up to 48 kHz. This capability ensures that sound reproduction remains clear and devoid of distortion, appealing to both casual users and audio professionals alike. Additionally, the chip supports multiple audio channels, making it ideal for gaming and multimedia applications where spatial audio is crucial.

Another significant feature of the YMF744B is its support for various audio formats, including PCM (Pulse Code Modulation), ADPCM (Adaptive Differential Pulse Code Modulation), and even MIDI. The versatility in format support allows users to interact with a broad spectrum of audio applications, from game design to music production.

The chip also comes with integrated Sound Blaster Pro compatibility, which significantly enhances its usability with a vast array of software and games designed during the 1990s and early 2000s. This compatibility is crucial for retro gaming enthusiasts who seek an authentic audio experience with classics from the past.

Moreover, the YMF744B champions power efficiency, making it an attractive choice for mobile computing platforms. Its low power consumption means that it can be effectively used in laptops without significantly draining battery life, allowing users to enjoy high-quality sound on the go.

In summary, the Yamaha YMF744B (DS-1S) stands out due to its advanced audio synthesis capabilities, high-quality playback features, and compatibility with multiple formats. These attributes make it a favored choice in the audio processing domain, continuing to impact computer audio technology long after its initial release.