ERS AirCool plus - Transmission Protocol

ERS
®
Manual / AirCool
®
plus -System / SP72_TA1C8 / -55°C +200°C / Ver. 02.02 35
9.3 Transmission protocol
As described in the settings above, the serial interface may operate with or without a
special transmission protocol.
If no protocol is selected, command strings are transmitted as ASCII characters, the
SP72 will send "ok" if the command is accepted or "?" if not accepted.
For a more safe communication the SP72 uses a transmission protocol with start-
and stop-flags and a checksum byte.
A message is of the following format:
STXMessageETXLRC
with STX (ASCII 02 Hex) acting as start-flag, ETX (ASCII 03 Hex) as stop-flag and
LRC as checksum byte, which is calculated as the XOR function over STX Message
ETX.
The protocol's handshake consists of the following procedure.
→ ENQ Request
← ACK if ready
← NAK if an error in transmission happens
after ACK the transmission of data starts
(i.e. STX Message ETX LRC is sent)
← ACK if received correctly
← NAK if error in transmission happens
← CAN if the received command is a unknown one
with: ENQ = ASCII 05 Hex
ACK = ASCII 06 Hex
NAK = ASCII 15 Hex
CAN= ASCII 18 Hex