1.1    Functions and Characteristics of the PA912 Module 
Unified Controller nv series PROFIBUS(PA912) Module Instruction Manual 
5 
 
CAUTION
TC-net I/O loop with PA912 should be a single loop 
configuration. When using Unified Controller type1   
or Unified Controller type2 with PA912, set the “
loop number” on the “module parameter”-“I/O 
loop” pane of the controller to “1”.   
 
Mandatory 
 
1.1.1  Cyclic transmission 
As the PROFIBUS master module, the PA912 module controls slave I/O devices 
(input  and  output  devices)  connected  via  the  PROFIBUS.  The  PA912  is 
controlled by the nv controller. The nv controller and the PA912 are connected 
via the TC-net I/O loop, and they have a virtually shared memory area called 
"common memory". When the output information is set in the common memory 
by the nv controller, the information is outputted to the PRIFIBUS slave output 
devices via the TC-net I/O loop. Similarly, the input information to the slave 
input devices is inputted in the nv controller common memory via the PA912 
and the TC-net I/O loop. 
 
 
Figure 1-2    Cyclic transmission 
nv controller 
(
)
 
 
 
 
Maximum
768W 
Maximum
768W 
35W 
Scan 
transmission
PROFIBUS 
slave I/O devices
Output 
device 
Input 
device 
Input 
device 
TC-net I/O loop 
common memory
TC-net I/O loop 
common memory
Output 
device 
I/O output
TC-net I/O 
loop