Dealing with faults (TSX CTY2C)

At a Glance

The TSX CTY2C module has two independent and additional functions, which can be configured by the user, for dealing with channel faults:

Storing is used to indicate occurrence of a fault, however temporary.
Masking certain faults enables the application to continue operating in downgraded mode.

These two functions are selected using the configuration screen.

Principle of fault storing

Storing is used to:

indicate to the application the occurrence of a fault, temporary or otherwise, shown by the channel error bit CH_ERROR (%Ir.m.c.ERR) and the module error bit MOD_ERROR (%Ir.m.MOD.ERR) (implicit exchanges),
and identify it via status words (explicit exchanges).

In the absence of a latch, there is a risk that temporary faults will not be detected in the regular scans by the processor, for these language objects are reset to zero as soon as the fault has disappeared.

Principle of masking faults

Masking involves preventing, according to the situation, channel error bits, module error bits and I/O and ERR LEDS being set. The faults concerned are selected individually (fault masking by default).

NOTE: In the event of an error whether masking was enabled or not, outputs will change to fallback mode to ensure safety, and the CH LED will flash.

Masked faults therefore risk being ignored by the application. Nevertheless, the application can access the fault warning if the test of the bit COUNT_FLT (%MWr.m.c.2.5) has been programmed.

Status words continue to be positioned normally, whether faults are masked or not.

Important notes

Even if a fault has been unmasked, it can pass unnoticed by the application if the store has not been configured, and if this fault is temporary.
There is also another parallel function which indirectly indicates faults linked to counting, using an Invalid measurement which has been detected.

Principle of reading and acknowledging faults

When the fault has been indicated to the processor, the latter must read the module status words using a READ_STS instruction.

Module status words are reset to zero when:

the fault(s) have disappeared,
and if there is a latch, after the acknowledgement command by the bit FLT_ACK (%Qr.m.c.3).