Maple Systems OIT Family - Manual (Page 44)

CHAPTER 4
PLC Register Monitors
The PLC’s registers and coils can be monitored, displayed, and updated by the OIT.
This is done by configuring the OIT screens to display PLC registers and/or coils as
embedded data fields (PLC Register Monitors). When the OIT displays a screen that
contains a PLC Register Monitor, the OIT reads the specified PLC register address and
then displays the data. If the PLC Register Monitor has been configured as read/write,
when the OIT operator changes the data in the PLC Register Monitor on the OIT’s
display the OIT writes the change to the PLC register address.
A maximum of 25 “read only” or “read/write” PLC Register Monitors can be displayed on
each Message, Alarm, Recipe, or Menu screen (Menu screens only accept read only PLC
Register Monitors). If more than one PLC Register Monitor is on a screen, each is updated
by the OIT in continuous succession as rapidly as possible within the constraints of the
particular PLC protocol and baud rate selected. Therefore, the update rate of each PLC
Register Monitor is determined by the number of PLC Register Monitors on the screen and
the PLC protocol being used (baud rate, protocol overhead, PLC program, etc.).
The arrow keys move the cursor from one read/write PLC Register Monitor to another.
Each time one of the arrow keys is pressed, the cursor moves to the next closest
read/write PLC Register Monitor in the direction of the pressed arrow key. When the
cursor is located at one of the edges of the display, additional keypresses in the direction
of the display edge cause the cursor to wrap around, from top to bottom, etc.
Once the cursor is positioned in the correct PLC Register Monitor, the OIT operator can:
• Press the TOGGLE key to alternate between “1” and “0” values in 1/0 Coil, On/Off Coil,
or ASCII String PLC Register Monitor formats. The data is sent to the PLC immediately,
so the OIT operator does not need to press the ENTER key.
• Press the DELTA+ and DELTA- keys to “jog” or adjust the value in the PLC Register
Monitor by preset increments. The data is sent to the PLC immediately, so the OIT
operator does not need to press the ENTER key. The preset increment is determined by the
system programmer. When the value in the PLC Register Monitor bumps against the
preset low or high limits, an error message is displayed and the delta keys are ignored.
• Press the CLEAR key to clear the PLC Register Monitor’s contents and activate data entry
mode. When data entry mode is activated, the PLC Register Monitor becomes blank and
the cursor moves to the rightmost character position. The OIT operator can then enter a
new value using the numeric keys on the OIT’s keypad. When finished, the OIT operator
presses the ENTER key. If the value is within the preset low and high limits, the entry is
accepted and immediately written to the PLC. If the value is outside the preset limits, an
error message is displayed indicating that the entered value is out of range.
NOTE:When the OIT operator enters data into a PLC Register Monitor that has the adjustable decimal
point enabled, the OIT operator does NOT enter the decimal point, but simply enters the raw
number. Once the data is sent to the PLC, the correct decimal position is shown.
PLC Register Monitors 44
1010-0099, Rev. 07