Rockwell Automation 1771-IS 5V DC INPUT MOD - Manual (Page 10)

Module Preparation, Wiring and
Installation
Chapter 2
2-3
momentary (latched) contact mode or maintained contact mode. (ON for
fast scan, OFF for normal scan.)
Switch #4 - Maintained Contact Mode/Momentary (latched) Contact
Mode. Select the maintained contact mode when storing the status, ON or
OFF, of maintained switch contacts. Their status is updated in every scan.
Select the momentary (latched) contact mode when storing momentary
OFF-ON switch contact transitions. Subsequent scans will not reset
latched bits even if the corresponding switches are reopened. The
transition is latched ON in module memory and must be reset after the
latched data is transferred to the processor. [ON for momentary (latched)
contacts, OFF for maintained contacts.] The position of SW #4 will also
affect data byte storage. See the diagrams in chapter 3 for further detail.
Switch #5 - Always OFF.
Switch # 6 - Always OFF.
Switch # 7 - Program Reset/Automatic Reset. Select program reset when
momentary (latched) switch status data is to be reset by setting a bit in a
user program instruction. Refer to section titled “Other Programming
Considerations, PLC-2 Family and PLC-3.” Select automatic reset when
momentary (latched) switch data is to be reset automatically. This switch
is not functional when the module is operating in the maintained contact
mode. (ON for program reset, OFF for automatic reset).
Important: When using momentary contact mode in remote applications,
only the program reset mode should be selected. Use program reset to
guard against loss of data during transfer to the processor. When using
momentary contact mode in local I/O applications, either the program
reset or automatic reset can be selected.
The allowable combinations of module operating modes are summarized
in Figure 2.2.