Maple Systems OIT Family (ASCII) - Manual (Page 54)

Function Key LEDs
The LEDs of the function keys can be individually programmed to be controlled by the OIT
or by the ASCII host. If a function key LED is programmed to be controlled by the OIT then it
operates as previously described (refer to the “Function Keys” section). If a function key
LED is programmed to be controlled by the ASCII host, then the LED reflects the current
value of a pre-programmed OIT coil register. The OIT reads the OIT coil register once every
second. If the coil is set, then the function key LED will turn on. If the coil is clear, then the
function key LED will turn off. Allowing the ASCII host to control the LED provides the
control systems engineer with more indicator LEDs that can be used for purposes other than
as visual feedback for the function keys.
Alarms
Refer to the Alarm Screens section.
Control Features
Timer Events
The OIT can be configured to set a coil in the OIT coil registers at a particular time during a particu-
lar day of the week or daily (example: set OIT coil register C100 every Monday at 10:30 a.m.). In
addition to setting an OIT coil register, the OIT can be configured to display a screen at that time
(example: display Screen #2 every Monday at 10:30 a.m.). This is known as a timer event. Up to 16
timereventscanbeprogrammedfortheOIT.TimereventsarecheckedbytheOITeveryminute.
Note: Timer events are only supported by the OIT3250, OIT4450, and OIT5400.
Real Time Clock Download to ASCII Host
For OITs with a real time clock (RTC), the current time and/or date can be sent to the OIT
data registers. This allows an ASCII host to take advantage of the clock that is in the OIT. Up-
dates of the OIT data registers occur every thirty seconds. The clock’s time will be sent to one
16-bit OIT data register. The hour (HH) of the day (in 24 hour format) is stored in the eight
most significant bits in BCD format. The minutes (MM) of the hour is stored in the eight least
significant bits in BCD format. For example, if the current time is 2:35 p.m., then the OIT
would send to the OIT data register the value 1435 (HHMM) in BCD format.
The clock’s date is sent to two 16-bit OIT data registers. The first register stores the month
and day of the month. The second register stores the day of the week and the year. All values
are in BCD format. For the first register, the eight most significant bits are used for the month
(MM). The eight least significant bits are used for the day of the month (DD). For the second
register, the eight most significant bits are used for the day of the week (DY). The day of the
week would be represented with a number from 1-7 with the number 1 representing Sunday,
the number 2 representing Monday, etc. The eight least significant bits are used for the year
(YY). For example, if the date of the clock were Wednesday, September 13, 1995, then the
OIT would send to the first OIT data register the value 0913 (MMDD) in BCD format and the
second OIT data register the value 0495 (DYYY) in BCD format. If both time and date are
checked, then three OIT data registers are used with the first register used for time and the
other two registers used for date.
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