UM0851 datasheet(199/245 Pages) STMICROELECTRONICS

199 / 245 page

UM0851

Audio/video drivers

Doc ID 16604 Rev 2

199/245

Figure 54.

TDM Cell

The switching feature uses a total of 2048 memory locations, each 8 bits wide. Switching

means that all the input timeslots of a frame received on the TDM are stored in the memory

and at the next frame, this data will be sent on the timeslot that is required to be switched.

Consider an example of switching: TS3 is switched with TS1021. It means that during TS3,

the TS3 content received on the DIN pin is stored at the 3rd byte of the storage part of the

switching memory while TS1021 of the previous frame (1021st byte of the reading part of

the switching memory) is played on the DOUT pin. During TS1021, TS1021 received on the

DIN pin is stored at the 1021st byte of the storage part of the switching memory while TS3 of

the previous frame (3rd byte of the reading part of the switching memory) is played on the

TDM output, allowing a phone call to be established between the caller connected on TS3

and the one connected on TS1021.

Figure 55.

TDM waveforms

8.2.2

Software overview

The TDM device driver sits on top of the TDM Controller and provides all necessary

functions for switching and bufferization.

The TDM software system architecture is represented in the Figure 56.

Switched

data

state

machine

Bufferized

data

state

machine

Switching

memory

Switching

memory

Buffer

memory

Buffer

memory

Action

memory

AHB

interface

DIN

DOUT

CLK

SYNC

Input

frame

Frame n

Frame n + 1

ITS0

ITSx

ITS31 ITS0

ITS31

ITSx

OTS0

OTS31

OTSy

y > x

Output

frame

UM0851 Datasheet(PDF) 199 Page - STMicroelectronics

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