FANUC Robotics America GFK-1535A - Manual (Page 45)

GFK-1535A Chapter 3 Operation 3-5
3
Input Data Format
When the NIU takes its turn on the bus, it sends one input data message containing
the latest values for all configured discrete inputs followed by all configured analog
inputs. Because they are broadcast, they can be obtained by any bus controller on
the bus.
Input Data Message
(up to 128 bytes)
discrete inputs analog inputs
Í Configured I Length О Н Configured AI Length Î
AI starting reference data I starting reference data
To CPU
⇐
The data lengths are equal to the lengths of I and AI data configured in the NIU.
Either length may be zero.
Discrete inputs appear in the input message in the same sequence as their assigned
input references. Each discrete input module occupies one byte per eight circuits.
Analog inputs are also in the same sequence as their input references. Each analog
input module occupies two bytes (one word) for each analog channel.
Input Defaults
If an input module is removed or fails to operate correctly, its configured default
state is substituted for actual input data. A diagnostic message is provided to
indicate loss of module. Forced input data is not affected.
I/O Data Handling by the PLC or Computer
How a PLC or computer handles input data from the NIU depends on its type:
T A VersaMax or Series 90 PLC places the data in the %I and %AI references
selected during PLC configuration. These must be the same references selected
during NIU configuration.
T A Series Six or Series Five PLC places the data into I/O table or register
memory. A beginning address in Series Six or Series Five I/O Table memory
can be entered during station configuration.
T A host computer with a PCIM places the data into the input table segment that
corresponds to the serial bus address (Device Number) of the NIU.