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FCP manual
Code +030220391 – rel 1.1 07/11/06 35
9.2.1 Description of the Function codes supported
• 0x01 Read Coils
• 0x02 Read Discrete Inputs
Return from 1 to 32 consecutive digital variables. The use of the two function codes is identical, as no distinction is made between Coils (read/write digital variables)
and Discrete Inputs (read only digital variables from I/O devices).
The slave responds with an Exception in the following cases:
EXCEPTION 2:
Address of the first variable requested > 32
Address of the first variable req number of variables requested > 32
EXCEPTION 3: Number of variables requested > 32
•
0x03 Read Holding Registers
•
0x04 Read Input Registers
Return from 1 to 16 consecutive analogue variables or from 1 to 32 consecutive integer variables.
The use of the two function codes is identical, as no distinction is made between Holding Registers (read/write Registers) and Input Register (read only Registers from
I/O devices).
To map the addresses of the analogue and integer variables (according to the standard Carel protocol) in the space of Modbus addresses, the following rule has been
defined:
Analogue variables (Carel range: 1-16) ->
Modbus range: Holding/Input Registers 1-16
Integer variables (Carel range: 1-50) -> Modbus range: Holding/Input Registers 101-150
The slave responds with an Exception in the following cases:
EXCEPTION 2:
Address of the first variable requested NOT between 1-16 and 101-150;
Address of the first variable requested between 1-16 and address of the first variable req number of variables requested > 16;
Address of the first variable requested between 101-150 and address of the first variable req number of variables requested > 150;
EXCEPTION 3: Address of the first variable requested between 1-16 and number of variables requested > 16;
Address of the first variable requested between 101-150 and number of variables requested > 32;
Note: the maximum number of 32 integer variables that can be sent is determined by the maximum size of the transmission buffer.
• 0x05 Write Single Coil
Writes a digital variable as ON or OFF to the Slave.
The slave responds with an Exception in the following cases:
EXCEPTION 2:
Address of the variable being written > 32;
EXCEPTION 3: Value being written contained in the Modbus package other than 0x0000 (OFF) or 0xFF00 (ON) (Note: a Write Single Coil package sent by a
Master compliant with the Modbus protocol should NEVER generate this exception);
EXCEPTION 4: The Master has attempted to write a read only digital variable;
•
0x06 Write Single Register
Writes an analogue or integer variable to the Slave.
The slave responds with an Exception in the following cases:
EXCEPTION 2:
Address of the variable being written not between 1-16 and 101-150;
EXCEPTION 4: The Master has attempted to write a read only analogue or integer variable;
The Master has attempted to write an analogue or integer value that is outside of the minimum and maximum range;
•
0x11 Report Slave ID
Returns the unit code (MAC parameter), the ON/OFF status of the controller (as there is no standby mode, the controller is always ON) and the FW release (REL
parameter).
The slave never responds with an exception.
For the addresses of the individual variables, see the “Modbus var” column in the table of parameters.