Watts LF007 Serie Instrucciones De Instalación página 13

Modbus RTU Functions
The Modbus RTU binary protocol uses a master-slave technique. Only the master device
can initiate transactions. The slave device responds by supplying the requested data to the
master or by performing the requested action in the query. The returned messages are
considered response messages.
Eight different functions of the protocol allow control of every function within the module. The
output data values are stored in registers and can be read by using either Function 03 or
Function 04.
The first input data register is located at register 40049. There are seven consecutive registers
(40049 to 40055) that contain the module data values (only registers 40049 to 40051 are
used for transmitting pressure data; additional input data registers are unused). The values
are stored in consecutive registers for fast reading of all the data values with one Modbus
function call.
FUNCTION
01
02
03
04
05
06
0F
10
Function 01 – Read Coil Status
Returns the coil status of discrete digital output points. A typical function 01 command and
response follow.
Command Usage
Address
Function
Addr HI
Addr LO
Data HI
Data LO
Response Message
Address
Function
Register Number
Data HI
Data LO
Data HI
Data LO
Error Check
DESCRIPTION
Return coil status of discrete output points
Read ON/OFF status of discrete inputs in the slave device
Read content of holding registers (4X references) in the slave device
Read content of input registers (3X references) in the slave device
Force state of a single coil (digital output) to either ON or OFF
Preset the state of a single register to a specific value
Force the state of a sequence of coils (digital outputs) to a specific state
Preset a sequence of registers (4X references) to specific values
One Byte Slave Address
One Byte Function Number
Starting Address HI Byte
Starting Address LO Byte
Typically ZERO
Number of bits, limited to 1..64
One Byte Slave Address
One Byte Function Number
Number of data bytes
Data Coils (27-20)
Data Coils (35-28)
Data Coils (43-36)
Data Coils (51-44)
Two Byte CRC
Returns four bytes typically.
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