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64 T1-16S User’s Manual
5. Operating System Overview
5.1 Operation modes
The T1-16S has three basic operation modes, the RUN mode, the HALT mode and
the ERROR mode. The T1-16S also has the HOLD and RUN-F modes mainly for
system checking.
RUN: The RUN mode is a normal control-operation mode.
In this mode, the T1-16S reads external signals, executes the user program
stored in the RAM, and outputs signals to the external devices according to
the user program. It is in the RUN mode that the T1-16S performs scans the
user program logic, which is the basic operation of a PLC.
Program changes and EEPROM write are possible while the T1-16S is in
the RUN mode. Refer to section 6.9.
HALT: The HALT mode is a programming mode.
In this mode, user program execution is stopped and all outputs are
switched off.
Program loading into the T1-16S is possible only in the HALT mode.
For the standard T1, program changes and EEPROM write are possible only
when the T1 is in the HALT mode.
ERROR: The ERROR mode is a shutdown mode as a result of self-diagnosis.
The T1-16S enters the ERROR mode if internal trouble is detected by self-
diagnosis. In this mode, program execution is stopped and all outputs are
switched off. The cause of the shutdown can be confirmed by connecting
the programming tool.
To exit from the ERROR mode, execute the Error Reset command from the
programming tool, or cycle power off and then on again.
HOLD: The HOLD mode is provided mainly for checking the external I/O signals.
In this mode, user program execution is stopped, with input and output
updating is executed. It is therefore possible to suspend program execution
while holding the output state. Moreover, a desired output state can be
established by setting any data by using the programming tool.
RUN-F: The RUN-F mode is a forced RUN mode provided for program checking.
This mode is effective when using the expansion I/Os.
Deferent from the normal RUN mode, the RUN-F mode allows operation
even if the registered I/O modules are not actually mounted.