Serial communication process

The transmitter carries out the following steps:

• Application sends AMS command
• If the AMS command is greater than 255 bytes, an error is sent to the application.
• An AMS serial frame is allocated and the AMS command is copied into the user data field. The user data length field is set to the size of the AMS command.
• The frame is sent via the serial interface and acknowledgement is waited for.
• In case the transmitter does not receive a valid acknowledgement after multiple transmission, then a reset frame is sent.

The receiver carries out the following steps:

The serial interface is exported in case data is received:

• Check the magic cookies
• Check the CRC
• Check whether the fragment number agrees with the internal counter. If this is the first received frame, or if no more frames are received after a certain time, then the frame number is simply accepted and not checked.
• If a valid frame has been received:
• Send an acknowledgement to the transmitter
• Forward user data ( AMS telegram) to the application

Since ADS is only a higher-level protocol from AMS, the same is also valid for the sending of ADS-commands. The ADS command is in the data range of the AMS commands, that can then be sent via the serial interface.