Specifications

61
Schneider Electric
The Modbus Protocol (continued)
Addressing
The addressing mode differs according to the module:
b With a code wheel:
v wheel no. 1 gives the most significant bit in addresses,
v wheel no. 2 gives the least significant bit.
b With a keyboard. The principal is the same, but the method may differ:
v parameter setting in a single operation,
v parameter setting in two operations (most significant / least significant).
In any case, always consult module implementation instructions.
Functions
Jbus functions:
b Function 1: Read n output or internal bits.
b Function 2: Read n input bits.
b Function 3: Read n output or internal words.
b Function 4: Read n input words.
b Function 5: Write 1 bit.
b Function 6: Write 1 word.
b Function 7: Fast read 8 bits.
b Function 8: Diagnostic of exchanges.
b Function 11: Read event counter.
b Function 12: Read trace buffer.
b Function 13: Read/write address > FFFFh or program command (downloading,
etc.).
b Function 14: Diagnostic associated with program commands.
b Function 15: Write n bits.
b Function 16: Write n words.
Each module has a single address on the
network. This address is between 1 and
255 (1 and FF in hexadecimal).
The value of this address is coded in one
byte. The value "0" is prohibited because it
is used only for broadcasting.
The Jbus protocol has 14 functions. Query
and response frames have a maximum of
255 bytes.
Guide to Integration
Modbus / Jbus