Atmel AT83SND2C MP3 - Manual (Page 18)

Communication Protocol
3-14 AT83SND2CMP3 User Guide
7525A–MP3–07/05
3.5 Error Management
3.5.1 Command Time-out When 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
3.5.2 Bad 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.
3.6 UART 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.
3.6.1 Polling 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.
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
.