Maple Systems OIT Family (ASCII) - Manual (Page 48)

Retentive Mode
The Retentive Mode option was designed for OITs that are communicating to PLCs. When
the OIT powers up in Retentive Mode, the OIT sets the current state of each function key (On
or OFF) according to the value of the corresponding Function Key coil in the PLC. For exam-
ple, if the Function Key coil reserved for function key #1 is on, then the OIT configures func-
tion key #1 for the on state.
For the ASCII Slave protocol, the Function Key coils reside in the OIT. These coils do not re-
tain their value when the OIT loses power. Therefore, the retentive mode feature cannot be
used for the ASCII Slave protocol.
Momentary Function Key
When configured using this option, the function key operates as a simple momentary (nor-
mally open) switch. Therefore, when the function key is pressed and held down, the corre-
sponding Function Key coil is set and remains set until the OIT operator releases the function
key. Similarly, the function key LED remains lit as long as the function key is pressed. The
OIT’s buzzer clicks once when the function key is pressed and then again when the function
key is released.
Push On/Push Off Function Key
When configured using this option, the function key operates as a simple on/off switch. It
sets the corresponding Function Key coil when pressed and clears it if pressed again. The
OIT’s buzzer clicks each time the function key is pressed. The function key LED operates in
the following manner according to how it is programmed:
On/Off
When the function key sets a coil, the LED is on. When the function key clears a coil, the
LED is off.
Off/On
When the function key clears a coil, the LED is on. When the function key sets a coil, the
LED is off. This setting might be used to represent a normally closed contact coil.
Blink/Off
When the function key sets a coil, the LED blinks at a rate of two blinks per second. When the
function key clears a coil, the LED is off.
Off/Blink
When the function key clears a coil, the LED blinks at a rate of two blinks per second. When
the function key sets a coil, the LED is off. This setting is most often used to represent nor-
mally closed contact coils.
Latch Function Key
This mode of operation allows a function key to be configured as a “latched” key. A latched key
is a function key that, whenever it is pressed, sets the corresponding Function Key coil. The
ASCII host is then responsible for clearing the Function Key coil when it deems appropriate. The
LEDassociated withthefunction key blinks momentarilywhenever the functionkey ispressed.
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