Rockwell Automation 2705 REDIPANEL KEYPAD MODULE USER MANUAL - Manual (Page 66)

Chapter 7
Programming
7–28
RediPANEL Modules have a standard TIMED feature that holds all push
button depressions for a minimum of 100 milliseconds to allow the PLC
controller to read the depression during its scan cycle. No special
programming is needed for this function. Most system configurations can
use this feature to help insure data capture of a push button depression.
As a general guideline, handshaking is not required. The few cases where it
is required would be:
1. Very lengthy scan times. Lengthy scan times can occur when the block
transfer instruction is used numerous times in the ladder program.
Lengthy scan times can also occur when the ladder program is very
large.
2. When the remote I/O link is approaching its physical limitation of 16
devices (RediPANEL push button modules, keypad modules, remote I/O
racks).
To select the Handshake feature, enable (set ON) the module’s DIP switch 7
on switch bank #2. Setting this switch OFF, gives you the TIMED feature,
which is the default setting. Chapter 5 discusses switch settings for mode
configuration. Figure 5.5 refers to Handshake enable and disable settings.
To use the Handshake feature, the PLC program must have a rung that
accepts the handshake bit and allows communication to continue. Refer to
Figure 7.11 for an example of this rung. If you have selected the Handshake
feature, then your PLC program must contain this rung, or the module will
not operate.
Figure 7.11
Ladder Logic Handshake Rung
17 17
Input Handshake Bit Output Handshake Bit
When to Use the Handshake
Mode