Rockwell-automation 1770, D17706.5.16 Ref Mnl DF1 Protocol Command Manual do Utilizador descarregar pdf (Página 61)

4–7Using Full-duplex Protocol to Send and Receive Messages

Publication

17706.5.16 - October 1996

How the Receiver Operates

The receiver must be capable of responding to adverse situations.

Some of the problems that can occur are:

• the message sink is full, so the receiver has nowhere to put

a message

• a message can contain a parity error

• the BCC or CRC can be invalid

• the DLE STX or DLE ETX BCC/CRC may be missing

• the message is too long or too short

• a false control or data symbol occurs outside a message

• a false control symbol occurs inside a message

• the DLE ACK response is lost, causing the transmitter to send a

duplicate copy of a message already passed to the message sink

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Rockwell-automation 1770, D17706.5.16 Ref Mnl DF1 Protocol Command Manual do Utilizador Página 61