Watchdog feature (R32-R33) IE2808
Via the Enable Default Status Register R32 and the Default Status Register R33 the behavior of the outputs for communication breakdown can be set:
- Register R32 activates or deactivates the watchdog feature.
- Register R33 defines for each single channel the switching state of its output in error case (if watchdog was activated).
For changing the register at first the write protection must be disabled. This is done by writing the user code word (0x1235) into register R31.
For using the watchdog feature pay attention, that at powering on the system no communication connection exists, that means the outputs are set to the pre-defined values.
Register | Description | Output | Description | default |
|---|---|---|---|---|
32 | Watchdog active | 00 - 15 | 1 = activated; 0 = deactivated | 0xFFFF |
Register | Description | Output | Description | default |
|---|---|---|---|---|
33 | Output State | 00 - 15 | 1 = ON; 0 = OFF | 0x0000 |
In delivery state the watchdog is activated and the pre-defined output states are set to 0. So all outputs are switched off in error case!
Example
Register 32 = 1111 1111 1111 1111
Register 33 = 1000 0000 0000 0000
Process data from the higher level controller = ON for all outputs
Now at a communication breakdown all outputs except output 16 are set to OFF. Output 16 is set to ON.