
22 840Hxl - Serial Protocol
8 Serial Protocol
The 840Hxl can be controlled via the serial port using the commands described in
this section. The following table shows the default communication parameters.
RS-232
Baud Rate: 9600
Data Bits: 8
Stop Bits: 1
Parity: None
8.1 Command Format
Commands must be in the following format:
0xEB, address, command, length of data, data 1, …data n, checksum
where the following table describes the command components.
Command
Component
Description
Device address. This is always 0x90 for the 840Hxl
How many bytes sent/received (from data 1 to data n)
data 1, data n One or more command variables within the range 0x01 to 0xFA and excluding 0xEB
checksum Optional—Checks whether the sending/receiving frame is valid.
Check sum = Address + Command + Data length + Data 1+…+Data n
For example, EBH, 90H, 01H, 01H, F3H, 85H
Check sum = 90H + 01H + 01H + F3H = 185H
Note: The checksum gets the low 8 bits, for example, if the check sum = EBH, then check sum =
8.2 Device Response
The device responds as follows:
0xEB, 0x90, command, 0x01, answer, check sum
where answer is one of the values described in the following table.
Command
Component
Description
0xF1 Either:
–the device received the wrong address and returns no response
–the device gets information about Errors and Alarms
The data is out of range. The command is not executed
0xF3 The device is currently controlled by the buttons. The command is not executed
0xF7 The data length is incorrect. The command is not executed
0xFC The data is out of range. The command is not executed
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