GE GFK-0825F Configuring Extra References in the BIU I/O Map, Example

GFK-0825F Chapter 5 Station Configuration 5-17
5
Configuring Extra References in the BIU I/O Map
Normally, there is no need t o configure extra I/O refer en ces in the BIU's network I/O map .
Although unused referen ces do not contain meanin g ful data, they do add to the Genius bus sca n
time.
One circumstance under which it might be best to configure extra I/O references would be to allow
for future addition of I/O modules to a station in a system where the host uses the same reference
addresses for data as th e BIU. In such a system, reserving extra references or leavin g vacancies at
configuration time can be a convenient way to prepare for future additions to a station. (In a
system where the BIU's refer ence addresses are not u s ed by th e host, changing the BIU's I/ O map
does not affect the host s o th ere is no need to configure unu s ed r efer ences for future modules. )
Input Data Message with Some Inputs Not Used
discrete inputs a nal og inputs
Configured I Length Configured AI Length
AI starting reference dataI starting reference data
To CPU
unused
discrete
references
unused
analog
references
Example
An application has two stations in a system where the host uses the BIU reference addresses.
Station 1
I0001 - I0064
AI0001 - AI0008
Q0001 - Q0032
AQ0001 - AQ0008
Station 2
I0065 - I0128
AI0009 - AI0016
Q0033 - Q0064
AQ0009 - AQ0016
At a later time, it becomes necessary to add a discrete input module to station 1. However, in
station 1, there are already enough input modules to use all of the assigned input references (I0001
- I0064). Ideally, the extra module would be added to station 1 at I00065, but that is already used
as a reference in station 2. The alternatives at this stage are:
1. Change the map of station 2 to free up the needed contiguous I references.
2. Change the map of station 1 to start at higher references, such as I0097 - I0160.
3. Add a third I/O station to accommodate the additional modules.
It would have been easier t o add the module to station 1 if extr a r efer ences had been configur ed
originally, or if some vacancies had been allowed, as shown below.
Station 1 Station 2
I0001 - I0096
AI0001 - AI0008
Q0001 - Q0032
AQ0001 - AQ0008
I0097 - I0160
AI0009 - AI0016
Q0033 - Q0064
AQ0009 - AQ0016