Usage Flow - Toshiba TMPR4925 Manual

14.3.3

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
Enable ENLINK
Check AC'97 status
Start up AC-link
Register setting such as Volume (*)
Setup DMA buffer
Configure DMAC
Start DMA Channel and
enable transmit-data DMA
Write to DMA buffer and update
DMA descriptor (repeatedly)
Stop updating DMA descriptor
Check completion status
Disable transmit-data DMA
Dummy write to data register to
clear pending DMA request if any
Disable ENLINK
(*) Register settings such as volume can be made during data playback.
ACLC and DMAC
Deassert ACRESET*
CODECRDY Interrupt
Start transmit-data DMA
Start sending data to slot
DMAC generates Transfer
Completion interrupt (repeatedly)
DMAC channel goes inactive
DMA underrun error occurs
Stop transmit-data DMA
Stop sending data to slot
Assert ACRESET*
Figure 14.3.3 Audio Playback Process Flow
14-5
Chapter 14 AC-link Controller
DAC Ready response
Start audio playback
Stop audio playback
AC'97
Start BITCLK
Set CODEC Ready
Set volume, etc.
Stop AC-link
Stop BITCLK