HI

I have designed a Tag group, there are about 50 tags and a modbus driver, a serial(TCP/IP) port in the group, each tag mapping to a same table to the real device.

After I copy tag groups and set different station ID,
When I connect to one device, all tags read values in one second,
when I connect to two device, some tags read values in one second, but some tags read values in two seconds.
when I connect to three or four device, some tags read values in one second, but some tags read values in four seconds, even 8 seconds.

I have setup the properties : ModiconVTSMaxBlock as 120, ModiconDigitalMaxBlockSize as 2000.

How do I increase the performance of read modbus device ?
(I have try using modscan to read those modbus device, every section about 100 address can be read in 300ms. )

The scan rate is set by the "Scan Interval" parameter of the tags and the driver will not go any faster than this interval.

Try setting this parameter to a very small value, e.g. 0.001, for all the Modbus tags.