I/O Server: Writing 3 Modbus registers in one operation

[JKSH]

Hello,

Can the I/O Server use Modbus Function Code 16 (preset/write multiple holding registers)? Essentially, my CompactRIO needs to send a 48-bit integer to a slave device, which means I need to write 3 registers.

I found a way to do it without I/O Server (http://zone.ni.com/reference/en-XX/help/370622M-01/lvmve/modbus_master_write_read_multiple_holding_r... ), but I was wondering if I could do the same using I/O Server.

Thanks!

[j_bou · Accepted solution]

Hello JKSH,

Unfortunately, a bound shared variable cannot read\write from 3 registers at once automatically. Below is a document which details Modbus I\O Server bound shared variable capabilities.

Using Modbus I/O Servers (DSC Module or Real-Time Module)
http://zone.ni.com/reference/en-XX/help/371618G-01/lvmve/dsc_modbus_using/

You do have the option to access two adjacent 16-bit input registers as one 32-bit shared variable but not 48-bit.

Regards, 

j_bou