Function Blocks
MBS Modbus Slave Function Block
Revision 11 HC900 Hybrid Control Designer Function Block Reference Guide 197
2/07
MBS Modbus Slave Function Block
Description
The MBS label stands for Modbus Slave Status. This block is part of the Communications category. It
looks like this.
Function
A communication function block that is internally assigned to optional Communication Port B that allows
the controller to act as a master device and communicate with slave devices using the Modbus protocol.
Requires one block per slave device, up to 32 devices maximum. Only one block may be assigned to each
slave device. It supports 4 read and 4 write parameters plus provides digital indication of communication
integrity.
Inputs
ENABLE = [ON] Slave device is in scan -
If the Enable pin IS connected, then enabling/disabling follows the state of the Enable pin of the block and
the enable/disable function on the diagnostic page of the HC Designer is grayed out
.
If the Enable pin is NOT connected, then the user must be in Monitor mode, Monitoring Serial Modbus
Diagnostics in the HC Designer, select the device to be enabled or disabled, and click the Enable (or
Disable) button.
EN1 through EN4 = [ON] Data value written once per scan
WR1 through WR4
= Values to be written to the selected register
ATTENTION
• This block does not support bit packing and single bit writing.
• If the register is an integer data type, the floating point input will be rounded up prior to
writing to the address register.
• Message Broadcasting is not supported on the UMC800.
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