Analog module diagnostics

At a Glance

A faulty module makes itself evident by means of lit or flashing RUN, ERR and I/O LEDs.

Faults are classed in three groups : external errors, internal errors and other faults.

External errors

There are two types of external errors which make the I/O LED light up:

Measurement range overrun fault

This fault occurs when the measurement taken on the input line is outside the user-defined limits.
Sensor link fault (only on TSX AEY 414/1614)

This occurs when there is a connectivity problem between the module and one or more sensors.

Internal errors

Each module carries out a series of self-tests (watchdog, memory, analog/digital conversion string, etc.).

When an error occurs during these tests, an internal error is signaled. The ERR LED lights up.

The table below shows the various self-tests performed by the modules and whether the processor sees a possible error :

Self-test performed	Status of LED ERR when an error occurs	Fault returned to the processor
Watchdog test	Permanently lit	no
EPROM memory checksum
X Bus interface test
External RAM test
EEPROM memory test
Converters test (1)		yes
Internal references test (2)		yes

Key :
(1) for the modules TSX AEY 414/1614
(2) for the modules TSX AEY 800/810/1600

If a module is inoperative and can no longer communicate with the processor, the latter is still informed about it by detection :

either by the absence of the module,
or by the fact that the module is switched off.

Other faults

The other faults include :

Terminal block fault

The terminal block fault occurs when at least one channel is used whilst the corresponding Sub-D connector or terminal block is missing.
External supply fault of the outputs (only with the TSX ASY 800)

The output supply fault occurs when an external supply is used to supply the module TSX ASY 800 and when this supply is detected as missing.
Communication fault

It can be caused by a hardware fault at rack back bus level, by a processor fault or extension cable fault.

NOTE: When there is a communication fault with the processor, the channel value images (at PLC processor level) are frozen at the last value present prior to the fault.

Fault diagnostics

The following table can be used to diagnose faults relating to the three LEDs: RUN, ERR and I/O :

Module status	Status LEDs
Module status	RUN	ERR	I/O
Normal operation
Module faulty or switched off
External errors: range under/overshoot external 24 V power supply fault
Internal error (module broken down): communication with CPU possible communication with CPU impossible
Other faults: communication fault terminal block fault

Key :
LED unlit
LED flashing:
LED lit:

NOTE: When a range under/overshoot fault occurs at the same time as a terminal block fault, the LEDs behave in the same way as for range under/overshoot (the I/O is lit).