Communication Protocol

3.5Error Management

3.5.1Command Time-outWhen a communication handling error occurs (for example data length does not corre- spond to the actual frame size), the AT83SND2CMP3 reception state machine is resetted after TimeResumeCommand ms.

If the Remote Controller does not receive any status from Player, it shall wait

TimeResumeCommand ms before sending the GET_STATUS frame.

Table 3-6 .Real Time Constraints Value

Items

Value

Description

 

 

 

TimeEffectiveCommand

400 ms max.

Maximum Time between Remote Controller

 

 

command and Player response before time-

 

 

out, exept for command: SYSTEM_RESET,

 

 

 

TimeResumeCommand

100 ms .

When a communication handling error occurs

 

 

(for example data length does not correspond

 

 

to the actual frame size), the

 

 

AT83SND2CMP3 reception state machine is

 

 

resetted after TimeResumeCommand ms.

 

 

 

3.5.2Bad CheckSum If Remote Controller sends command with bad checkSum: there is a Player Answer Acknowledge with Command Error. Remote Controller has to retry the command.

3.6UART Layer

UART Physical layer is:

–RXD signal

–TXD signal

The data byte consists of 10 bits:

„1 start-bit

„8 data-bit

„1 stop-bit

Serial data is transmitted on the TXD pin and received on the RXD pin.

UART default baudrate is 111 111 bps (physical baudrate, correspond to 115200bps - 3.5% error).

Note: To connect Remote Controller and AT89RFD-08 boards, please refer to Hardware User’s

Guide Boards and check Rx and Tx signals are crossed for each board.

3.6.1Polling Strategy The protocol implementation does not allow the Player to initiate the communication or to indicate its status update. Therefore, the Remote Controller shall have a polling management using the GET_STATUS command to get the up-to-date Player status. Refer to Table 5-1 . Player STATUS Description.

Here is a the principle of use of the communication protocol with UART layer:

–Remote Controller sends GET_STATUS command to Player,

–Player answers ACK_STATUS to Remote Controller to inform about its status.

3-14

AT83SND2CMP3 User Guide

7525A–MP3–07/05