Hello,

we are doing communication using modscan software with our MODBUS RTU RS485 based device. We are sending query through Modscan. Format of query from Modscan is explained below.

01 03 0000 0002 c40b

in above query

01 is my device address.
03 is READ command.
0000 is starting location of process varibale of
which we want to read value.
0002 is the length of data which i want to read.
c40b is CRC.

For above query format we are selecting 03:Holding Register as a MODBUS POINT TYPE
9600 is Baudrate
8 bits Data bits
1 Stop bit
None Parity

Using above query format we are getting proper data but now we want to do communication with ODD PARITY. In selection of communication parameters we are selecting ODD PARITY option for sending query to device.

But......

1. How my device will come to know that the
communication is with ODD Parity?

2. How to detect ODD Parity bit from query?

 

Parity is redundant and never normally used WHEN CRC error checking is implemented. Parity is not part of the protocol, it is handled by hardware (the UART). If you insist on enabling parity for Modbus RTU protocol, then you must choose 8 data bits. In other words, the UART must produce a start bit, 8 data bits, a parity bit and a stop bit.