register reading

Hi experts,

I need to read registers from an multidransducer with MODBUS RTU USING RS485 port. I have do connection point 8 of( DB9 RS485)OF VIPA PLC to point A of RS 485 of transducer and point 3 of (DB9 RS485) of VIPA with point B of transducer .I am using VIPA plc speed7. I am using winplc7 software from VIPAI have download from vipa library functions block SFC 216, SFC 218, and FB 72 with instance block DB 72 .I have do parameterize SFC 216 AND SFC218 in DB10 and FB72 with DB72. I have write in MB_DATA_PTR P#M 100.0 word 100,When I start program the status of SFC 216 and SFC 218 are
0000h and status of FB72 pulse from 7004h to 7006h but I can not see any value at flag area and MB_DATA_PTR in DB72 block is (?.)The data type of
transducer that I want to read are type T5 with address 30105-30305. the parameter of transducer are address 33, baudrate115200, parity none,number of bit 8,stop bit 2. I will appreciate your expert suggestion.
I'm not so sure there is a universally accepted standard for RS-485 pinout for DB9 connectors.

Best to follow the VIPA PLC's manual. For example, this one specifically calls out pins 3 and 8.[{"num":366,"gen":0},{"name":"Fit"}]

The important thing to note is that A and B markings are not consistent among vendors. The VIPA PLC uses B as the positive (non-inverting) signal and A as the negative (inverting) signal. Other equipment may use A as the positive and B as the negative. Try swapping your A and B lines.