Rta - Real Time Clock Adjust Instruction - Allen-Bradley MicroLogix 1400 Instruction Manual

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RTA - Real Time Clock
Adjust Instruction
RTA
Real Time Clock Adjust
Instruction Type: output
Execution Time for the RTA Instruction
When Rung Is:
Controller
True
MicroLogix 1400 999.8510 µs
The RTA instruction is used to synchronize the controllers Real-Time
Clock (RTC) with an external source. The RTA instruction will adjust the
RTC to the nearest minute. The RTA instruction adjusts the RTC based on
the value of the RTC Seconds as described below.
The RTA instruction will only change the RTC when the RTA rung is
IMPORTANT
evaluated true, after it was previously false (false-to-true transition). The
RTA instruction will have no effect if the rung is always true or false.
RTA is set:
• If RTC Seconds are less than 30, then RTC Seconds is reset to 0.
• If RTC Seconds are greater than or equal to 30, then the RTC
Minutes are incremented by 1 and RTC Seconds are reset to 0.
The following conditions cause the RTA instruction to have no effect on
the RTC data:
• RTC is disabled
• An external (via communications) message to the RTC is in progress
when the RTA instruction is executed. (External communications to
the RTC takes precedence over the RTA instruction.)
To re-activate the RTA instruction, the RTA rung must become false, and
then true.
There is only one internal storage bit allocated in the system for this
TIP
instruction. Do not use more than one RTA instruction in your program.
You can also use a MSG instruction to write RTC data from one controller
TIP
to another to synchronize time. To send (write) RTC data, use RTC:0 as the
source and the destination.
Function Files
False
0.4090 µs
Publication 1766-RM001A-EN-P - October 2008
59