MODBUS_MASTER (193)

MODBUS_MASTER (193)

ID                          193

Group: I/O

Short description:

Function that exchanges the indicated registers via the modbus protocol with the selected slave device on the RS485 bus.

Inputs (1):

Outputs (3):

Settings:

Function operation:

The MODBUS_MASTER function communicates with external devices via the Modbus protocol. There are 6 functions in the block that can be used to send or receive data.

Function 01 - ReadCoils reads any markers of the slave device. The block can operate in two configurations. The first is to impulse the block. If 1 appears at the input of the block, the block sends a query to the slave device for selected markers, after receiving the answer, the registers are copied to the selected controller markers. If another impulse appears at the input of the block, the block will be executed if the previous communication has been completed or the time for response has expired. The second configuration is to set 1 to the block input permanently. The block in this configuration works similarly to the above one, the only difference is that the block starts the next data reading cycle automatically at the end of the previous one.

Function 03 - ReadHoldingRegisters reads any registers of the slave device. The block can operate in two configurations. The first is to impulse the block. If 1 appears at the input of the block, the block sends a query to the slave device for selected registers, after receiving the answer, the registers are copied to the selected controller registers. If another impulse appears at the input of the block, the block will be executed if the previous communication has been completed or the time for response has expired. The second configuration is to set 1 to the block input permanently. The block in this configuration works similarly to the above one, the only difference is that the block starts the next data reading cycle automatically at the end of the previous one.

Function 05 - WriteSingleCoil enables writing a single marker to a slave device, the number of markers in this case will always be equal to 1. The block can operate in two configurations. The first is to impulse the block. If 1 appears at the input of the block, the block sends a query to the slave device for selected markers, after receiving the answer, the registers are copied to the selected controller markers. If another impulse appears at the input of the block, the block will be executed if the previous communication has been completed or the time for response has expired. The second configuration is to set 1 to the block input permanently. The block in this configuration works similarly to the above one, the only difference is that the block starts the next data reading cycle automatically at the end of the previous one.

Function 06 - WriteSingleRegister enables writing a single register to a slave device, the number of registers in this case will always be equal to 1. The block can operate in two configurations. The first is to impulse the block. If 1 appears at the input of the block, the block sends a query to the slave device for selected registers, after receiving the answer, the registers are copied to the selected controller registers. If another impulse appears at the input of the block, the block will be executed if the previous communication has been completed or the time for response has expired. The second configuration is to set 1 to the block input permanently. The block in this configuration works similarly to the above one, the only difference is that the block starts the next data reading cycle automatically at the end of the previous one.

Function 15 - WriteMultipleCoils is designed to send any number of markers. The block can operate in two configurations. The first is to impulse the block. If 1 appears at the input of the block, the block sends a query to the slave device for selected markers, after receiving the answer, the registers are copied to the selected controller markers. If another impulse appears at the input of the block, the block will be executed if the previous communication has been completed or the time for response has expired. The second configuration is to set 1 to the block input permanently. The block in this configuration works similarly to the above one, the only difference is that the block starts the next data reading cycle automatically at the end of the previous one.

Function  16 - WriteMultipleRegisters is designed to send any number of registers. The block can operate in two configurations. The first is to impulse the block. If 1 appears at the input of the block, the block sends a query to the slave device for selected registers, after receiving the answer, the registers are copied to the selected controller registers. If another impulse appears at the input of the block, the block will be executed if the previous communication has been completed or the time for response has expired. The second configuration is to set 1 to the block input permanently. The block in this configuration works similarly to the above one, the only difference is that the block starts the next data reading cycle automatically at the end of the previous one.

During the communication, the busy output is turned on. The error and err_id outputs are activated when errors occur. The table with the description of the errors is presented below:

Notes:

• For the controller in version 4s2a, you can address from 1 to 127 slave devices
• In the 4s2a version of the controller, the functions intended for the management of inputs / outputs operate only on the markers
• In the 4s2a version of the controller, the permissible range of modbus addresses is from 0 to 65535
• In the 4s2a version of the controller, the permissible range of controller register addresses is from 1 to 5000
• In the 4s2a version of the controller, the permissible range of controller marker addresses is from 1 to 2000
• In the 4s2a version of the controller, the maximum number of controller registers / markers and modbus registers is 800

R registers and M markers used:

The block uses user-defined registers in the block settings.