According to the Modbus standard, the character length in the Modbus RTU mode should be 11 bits and in Modbus ASCII mode 10 bits. It is possible to freely define the character parity: even, odd or no parity. No parity means that the bit length of the serial character is reduced by one. Thus, the character is compensated with an additional stop bit.
| Coding system | 8-bit binary |
|---|---|
| Bits per character |
1 start bit 8 data bits, the least significant bit is sent first 1 bit for even/odd parity; no bit if parity is not used 1 stop bit if parity is used; 2 stop bits if parity is not used |
| Coding system | Two ASCII characters representing a hexadecimal number |
|---|---|
| Bits per character |
1 start bit 7 data bits, the least significant bit is sent first 1 bit for even/odd parity; no bit if parity is not used 1 stop bit if parity is used; 2 stop bits if parity is not used |