UM0851 datasheet(198/245 Pages) STMICROELECTRONICS

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Audio/video drivers

UM0851

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Doc ID 16604 Rev 2

8.1.7

References

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linux-2.6.27/Documentation/fb/framebuffer.txt

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linux-2.6.27/Documentation/fb/internals.txt

8.2

TDM driver

This driver controls the TDM hardware block, which is present in SPEAr300 only.

8.2.1

Hardware overview

Time-division multiplexing (TDM) is a type of digital or (rarely) analog multiplexing in which

two or more signals or bit streams are transferred apparently simultaneously as sub-

channels in one communication channel, but are physically taking turns on the channel. The

time domain is divided into several recurrent timeslots of fixed length, one for each sub-

channel. A sample byte or data block of sub-channel 1 is transmitted during timeslot 1, sub-

channel 2 during timeslot 2, etc. One TDM frame consists of one timeslot per sub-channel.

After the last sub-channel the cycle starts all over again with a new frame, starting with the

second sample, byte or data block from sub-channel 1, etc

The TDM block includes the switching and bufferization functions of the Telecom IP. The

external TDM port supports synchronous data transfer. Each frame has a programmable

length and can support up to 1024 timeslots in full duplex. Data is synchronized by the bit

clock and a frame synchronization delimits frames that contain a programmable number of

timeslots. Each timeslot (8 bit data) can be used for switching or bufferization. Action

memory informs about what to do with each timeslot. It is a dual port memory connected

both to the module and the AHB.

Switching means that an output timeslot (a timeslot played on the DOUT pin) contains the

data received during the previous frame on an input timeslot (a timeslot received in the DIN

pin). Switching data is stored in a single port Switching Memory without access from AHB.

Bufferization means that data from DIN pin (one to four timeslots) is stored in the buffer

memory during a programmable number of frames and data from buffer memory is played at

the same time. The buffer memory is shared between the module and the AHB and split into

two banks. Up to 16 channels (buffers) can be stored/played from different buffers. Using 16

channels of 4 bytes allows 30 ms data storage for each channel as required by VoIP

applications. The block diagram of the TDM is shown in Figure 54.

CONFIG_FB_CFB_COPYAREA

This option includes the cfb_copyarea

function for generic software area copying.

CONFIG_FB_CFB_IMAGEBLIT

This option includes the cfb_imageblit

function for generic software image blitting.

Table 51.

CLCD configuration options (continued)

Configuration option

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