Rockwell Automation 2705 RediPanel Push Button Module - Manual (Page 60)

Chapter 4
Programming the RediPANEL Modules
4–21
RediPANEL Modules have a standard TIMED feature that holds all push
button depressions for a minimum of 100 milliseconds allowing the PLC to
read the depression during its scan cycle. No programming is required.
Most system configurations use this feature to insure data capture of a push
button depression.
Handshaking is required only under certain conditions.
1. Lengthy scan times. Lengthy scan times occur when the block
transfer instruction is used numerous times in the ladder program.
Lengthy scan times also occur with large ladder programs.
2. When the remote I/O link is approaching its physical limitation of 16
devices (RediPANEL modules, keypad modules, remote I/O racks).
To select the Handshake feature, enable (set ON) the module’s DIP switch 7
of Switch Bank #2. Setting this switch OFF, gives you the TIMED feature,
which is the default setting. Chapter 2 discusses switch settings for mode
configuration. Figure 2.3 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. Figure
4.8 shows an example rung. Your PLC program must contain this rung or
the module will not operate.
Figure 4.8
Ladder Logic Handshake Rung
17 17
Input Handshake Bit Output Handshake Bit
If handshake is enabled and the handshake rung is in the user’s program, the
RediPANEL module holds all push button input signals high for a minimum
of one complete PLC program scan. The signal(s) remain high for one
complete cycle of the handshake input bit. The handshake input and output
signals continuously toggle independent of any push button closures. The
handshake function is operational even if no push buttons have been pressed.
Handshake Mode