CTI Products IOB I/O Interface - Manual (Page 20)

IOB Hardware Reference Option Switches and Jumpers
CTI Products, Inc.
68-11168-105
15
The Select A Invert switch (OPTION switch position 3) is only used when
operating modes 2, 3 or 4 are selected (in mode 1, this switch is not used). The
switch is defined as:
Option Switch 3 Function
DOWN Inverted Select A Outputs (active low)
UP Normal Select A Outputs (active high)
This switch only affects the Select A output lines. All other Select output lines
are active low. Refer to section 3 for a discussion of each operating mode.
The I/O Scan Rate Select switch (OPTION switch position 4) is used to select the
I/O scan rate for the IOB module. The switch is defined as:
Option Switch 4 Function
DOWN Normal scan rate (3 times per second)
UP Fast scan rate (10 times per second)
The default position for this switch is DOWN, selecting an I/O scan rate of 3
times per second. For special applications, you may want to increase the scan rate
to the fast scan rate (10 scans of the I/O per second). This allows the IOB module
to detect inputs that are changing more than 3 times per second. The disadvantage
of using the fast scan rate is that the IOB module can generate more network
traffic since it will transmit a network message every time it detects an input
change. With the fast scan rate selected, the IOB module could generate 10
messages per second, instead of 3 messages per second when using the normal
scan rate. If an IOB module is generating more than 3 messages per second, you
may see overall system performance problems (such as slower system response or
missed events on other MCN modules) because other MCN modules may not be
able to communicate over the network as often. Therefore, if you have IOBs in
your system that are set to the fast scan rate, and you begin to experience slow
system response or missed events on other MCN modules, you will have to
change your IOBs to normal scan rate.
Jumper Options
Figure 3 shows the configuration of the two jumper options available on the rear
of the IOB. These jumpers should be installed at system installation time with
power removed from the IOB.