Filter
Top Products
GFK-0825F Chapter 5 Station Configuration 5-17
5
Configuring Extra References in the BIU I/O Map
Normally, there is no need to configure extra I/O references in the BIU's network I/O map.
Although unused references do not contain meaningful data, they do add to the Genius bus scan
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 the BIU. In such a system, reserving extra references or leaving vacancies at
configuration time can be a convenient way to prepare for future additions to a station. (In a
system where the BIU's reference addresses are not used by the host, changing the BIU's I/O map
does not affect the host so there is no need to configure unused references for future modules.)
Input Data Message with Some Inputs Not Used
discrete inputs analog 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 to add the module to station 1 if extra references had been configured
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