step 5 - cpu 115u and remote et 100u communication fault

My hardware configuration is one 115 cpu u get I / O from 2 remote stations (ET 100 Distributed I / Os). This 2 remote stations (ET 100u) connect with separate 2 serial links via 308-3UA12 Expansion Unit Interface Module. 

 My fault IS I can not operate  2  et100 u stations Simultaneously .At one time this can operate only one.This Means i stop one manually by ON / OFF switch, then other station can ON.Then i ON the OTHER off station there flashing I / O disable bulb in red. Here I attach i stack and B stack and hardware configuration .

And other is  

In remote stations there display inputs(flash in green) , but after check i online cpu via step 5 software there not display the ' 1 ' statues .

My understanding figure is erase eprom program on 308-3UA12 Expansion Unit Interface Module  .Can it happen ..???  

Can u send me sir COM ET 100 communication software ??? I couldn t  find this software from internet.