Hi, I have a similar problem. The communication stops sometimes, but if I make download of the program (with a diferent parameter, as data lenght, for example) the CPU back to communicate.

I'm using an ET200SP (CPU 1510SP-1 PN) and the Modbus_Master block hasn't the Disconnect function. How to resetting Modbus_Master in the ET200SP?

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Split from Modbus_master freezing in Busy.

Hello,

in this case I see problem with program logic. Simply you can set/reset your REQ input of Master instruction as you need. Also EN input you can connect via some bit memory if you need.

Duris_I

Hello,

in this case I see problem with program logic. Simply you can set/reset your REQ input of Master instruction as you need. Also EN input you can connect via some bit memory if you need.

 Duris,

   This is exactly what I have done with a MB_Master which BUSY freezes in high for indefinite time. Problem is, it doesn't reset. When I connect the EN again, busy is still true. The only thing that's worked for me is reloading the block to PLC with different parameter.

   Any idea why BUSY freezes?

Regards,

Hello,

for most cases I don't recommend set EN input of instruction via some condition, leave it joined completely as always true. Look to comm_load instance DB where you can also see other static tags which can change functionality of Master f.ex. how many repeats Master makes in case of not responding Slave, then error Slave not responding will be set. Also other static variables are also in Master instance DB, especially in my opinion Blocked_Proc_Timeout which can reset Activity of Master block. Really hard to say why BUSSY output is on, you can prior check functionality with f.ex. some MB PC application to see real respond times from real Slave and set optimal values in your PLC code. Just another opinion, I'll be set always big enough timeout for Slave to have proper answers.