6F3B0250
Basic Hardware and Function 89
5. Operating System Overvi ew

Self-diagnosis:

Checks the proper operation of the T1/T1S itself. If an error has detected and cannot be
recovered by re-t r ies, t he T1/T1S m oves int o ERRO R m ode. For the self-diagnosis
items, r efer to sect ion 10. 2.

Mode control:

Checks the mode control switch status and the mode control req uest commands fr om
the prog r am m ing tool.
The scan mode - floating scan or fixed-time scan - is also cont r olled hear .

Program check:

At the beginning of the RUN mode, the user pr ogram is com piled and its validity is
checked.

I/O update:

Reads the external input signals into the external input devices/r egisters (X/XW), and
sends the data of the external output devices/registers (Y/ YW) to the external output
circuits. Then the outputs ( r elays, etc. ) changes the states and latches unt il t he next I/O
update timing .
The stat es of the forced input devices are not updated by this oper at ion.

Timer update:

Updates the tim er r egisters which are activated in the user program, and t he timing
devices (S040 to S047).
NOTE The floating scan:
When one scan is finished, immediately starts the next scan. The scan time is
shortest, but may vary depending on the program execution status.
The fixed-time scan:
The scan operation is started every user-specified time. The time setting range
is 10 to 200 ms (10 m s unit s ) . If an actual scan needs longer time than t he
setting time, it works as t he floating scan.
Scan timeScan time Scan time
Scan time (50 ms fixed) Scan time (50 ms fixed)
(idling) (idling)
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