User Manual

Chapter 1 Introduction 5
Mode RTU ASCII
Coding System
8-bit binary.
Two hexadecimal
character contained in
each ASCII character of
the message
Hexadecimal.
One hexadecimal
character contained in
each ASCII character of
the message
Bits per Byte
1 start bit,
8 data bits,
1 bit for even/odd parity;
no bit for parity
1 stop bit if parity is used;
2 bits if no parity
1 start bit ,
7 data bits,
1 bit for even/odd parity;
no bit for parity
1 stop bit if parity is used;
2 bits if no parity
Error check
CRC LRC
1.2.3 Modbus/ASCII
When using ASCII mode, each 8-bit byte in a message is sent as two
ACSII characters. The primary advantage of this ASCII mode is that it
allows time intervals of up to one second to occur between characters
without causing an error.
Table 1-1 Comparison of Modbus RTU and ASCII mode