RCVDP SENDDP safety signals transfer timeout or SUBS_ON

Hi All

I had a situation where SENDDP declared no errors or Timeout (10Hex) error 

and SUBST_ON was high.

The RCVDP / SENDDP is for safety data transfer between 2 PLCs via Profinet or Profibus

(Coupler or master PLC to slave (IODEVICE) PLC.

The above behaviour was caused by other tag overwritting part of safety data.

Example

safety telegram is 6 bytes in / 12 bytes out or vice versa

and it was declared from let's say I / Q 2000 (occupies I2000..I2011 and Q2000..Q2005)

if you have an UDT declared as outouts let's say from 2010 (should be 2012)

compiler will not flag any faults. Software compiles / downloads OK but

the above functions will exhibit behaviour described above.
Moving UDT variable (standard) to 2020 solved the problem.

Also remember you will need 2 network unique ID numbers for DP_DP_ID argument

one number for your send / partner receive

another number for your receive / partner send

these numbers must not be used for any other transfers in the network

example

your PLC                         Partner PLC

RCVDP.DPDP_ID=1      SEND_DP.DPDP_ID=1
SEND.DPDP_ID=2        RCV_DP.DPDP_ID=2