7
1-2
System Configuration
Depending on your control requirements, you can combine various Units for
a total number of I/O points ranging anywhere from 20 to 148.
A P-type PC consists of a CPU Unit plus one or more of the following Units:
Expansion I/O Units, Analog Timer Units, Analog I/O Units, or an I/O Link
Unit. All of these Units are connected in series with the CPU Unit at one end.
An I/O Link Unit, if included, must be on the other end (meaning only one I/O
Link Unit can be used) and an Analog Timer Unit cannot be used with. The
rest of the Units can be in any order desired. The Units from which P-type
PCs can be built are shown below.
Unit type
Name
Words
occupied
Inputs
provided
Outputs
provided
CPU
C20P
2
12 points
8 points
C28P
2
16 points
12 points
C40P
4
24 points
16 points
C60P
4
32 points
24 points
Expansion I/O Unit
C4K
2
4 input points or 4 output points
C20P
2
12 points
8 points
C28P
2
16 points
12 points
C40P
4
24 points
16 points
C60P
4
32 points
24 points
Special I/O Units
Analog Timer Unit
2
4 timer inputs
C4K Analog Input Unit
2
4 analog inputs
C1K Analog Input Unit
2
1 analog input
Analog Output Unit
2
1 analog output
I/O Link Unit
2
16 input and 16 output bits
When determining which configuration to use, another factor to consider is
the ease with which I/O points can be assigned. In order to make the process
as simple as possible, it is recommended that a CPU be used which has
more I/O points than the largest Expansion I/O Unit. For example, rather than
combining a C20P CPU with a C20P Expansion I/O Unit, it would be prefer-
able to use a C40P CPU. Similarly, combining a C60P CPU with a C40 Ex-
pansion I/O Unit would be better than using a C40P CPU and a C60P Expan-
sion I/O Unit.
The tables on the following pages show the possible configurations for a
P-type PC. Although the tables branch to show the various possibilities at
any one point, there can be no branching in the actual PC connections. You
can choose either branch at any point and go as far as required, i.e., you can
break off at any point to create a smaller PC System.When implementing a
system there is a physical restriction on the total cable length allowable. The
sum of the lengths of all cables in the system must be limited to less than 1.2
meters.
The tables also show I/O word allocations for the Units in the systems and
which words will be input words and which words will be output words. All of
these are determined by the position of the Unit in the configuration except
for the C4P and C16P Expansion I/O Units, in which case the model of the
Unit determines whether the words are input or output.
System Configuration
Section 1-2
