TX4939 Datasheet, PDF (653/756 Pages) Toshiba Semiconductor – 64-Bit TX System RISC

ACLINK
Toshiba RISC Processor
TX4939
24.3.2. Usage Flow
This section outlines a process flow when using the AC’97 connected to ACLC. Refer to the subsequent sections for the
details of each operation performed in this process flow. The diagrams below describe the audio playback and recording
processes. The modem transmission and reception can be done in a similar way.
System Software
ACLC and DMAC
AC’97
Enable ENLINK
Deassert ACRESET*
24
Start BITCLK
Check AC’97 status
Start up AC-link
Register setting such as Volume
(*)
Setup DMA buffer
CODECRDY Interrupt
Set CODEC Ready
DAC Ready response
Set volume, etc.
Configure DMAC
Start DMA Channel and
enable transmit-data DMA
Start transmit-data DMA
Write to DMA buffer and update
DMA descriptor (repeatedly)
Start sending data to slot
DMAC generates Transfer
Completion interrupt (repeatedly)
Start audio playback
Stop updating DMA descriptor
DMAC channel goes inactive
Check completion status
Disable transmit-data DMA
Dummy write to data register to
clear pending DMA request if any
DMA underrun error occurs
Stop transmit-data DMA
Stop sending data to slot
Stop audio playback
Disable ENLINK
Assert ACRESET*
Stop AC-link
Stop BITCLK
(*) Register settings such as volume can be made during data playback.
Figure 24-4 Audio Playback Process Flow
Rev. 3.3 May 18, 2007
24-5