MODBUS COMMUNICATION IM151-8PN/DP

Dear Expert,

 I have attached two program back up IM151-8PN/DP 1. Modbus Ok and 2. Modbus Fail.

In 1st backup I have configured one modbus slave and VFD's on Profinet the MODBUS communication is ok. some times it breaks but for fraction of sec. it shows error (MODBUS time out on MODSCAN).

In 2nd backup I have configured One modbus slave and VFD, SImocode on Profinet and PAC3200, ACB on profibus then i checked modbus communication it shows max time MODBUS time out On MODSCAN 

also on HONEYWELL SYSTEM.

IN both PLC programs blocks are identical but I have changed Hardware configuration.

  Why this is happening ???. and What can i do to overcome this.

Please help me. 

Thanks and regards,

amsd

Dear All,

       I resolved the problem.Possibly the block need much time for the communication, then i changed the module to a 32 Byte-module, by this the datachange between the module and the CPU is fatser and slave could answer in  a shorter time.

Thanks for all your support.