B&B Electronics I-7011 Dual Watchdog Operation, Digital Input and Event Counter, Digital Output

3.3 Dual Watchdog Operation

Dual Watchdog = Module Watchdog + Host Watchdog

The Module Watchdog is a hardware reset circuit to moni- tor the module’s operating status. While working in harsh or noisy environment, the module may be down by the external signal. The circuit may let the module to work continues and never halt.

The Host Watchdog is a software function to monitor the host’s operating status. Its purpose is to prevent the network/com- munication from problem or host halt. While the timeout occurred, the module will turn the all output into safe state to prevent from unexpected problem of controlled target.

The I-7000 module with Dual Watchdog may let the con- trol system more reliable and stable.

3.4 Digital Input and Event Counter

The digital input DI0 may work as event counter. The counter updates while the input changes from high level to low level. The counter is 16-bit width and useful for low speed count, frequency is lower than 50Hz.

3.5 Digital Output

When the module power on, the host watchdog timeout flag is checked first. If the status is set, the digital outputs (DO0 and DO1) of module will set to Safe Value. If the flag is clear, the digital outputs will set to PowerOn Value.

If the host watchdog timeout flag is set, the module will ignore the digital output command @AADO(Data).

62 I-7011, I-7018 User Manual Rev:B1.0