TECHNICAL NOTE - DT5

Refer to Drawing No. RMS4185A and locate the pulse input (pin 7 of the event input connector J6).

DESCRIPTION

This input has a high impedance (> 10 Kohms) and relatively low hysteresis (70 mV) and as a result, can cause problems due to noise in certain installations.

A noisy input could cause an excessively high number of interrupts to be generated for the main processor and as a result, a "crash" may occur. The most likely indication of this condition is the following error messages:

'STACK NEAR OVERFLOW'
or 'STACK OVERFLOW'.

With a 'STACK OVERFLOW' condition, it is impossible to resume operation, and a RESET is required. The message will probably repeat when scanning is resumed.

The above condition can occur even though 'Doppler' is not selected as a Scan source.

To avoid this problem, observe the following:

1. If this signal input is not used, wire this pin to ground (refer to Drawing No. RMS4185A for the connector pinout).

2. If it is used, it should be ensured that no ringing or noise occurs during transitions.

3. The event input connector should not be connected or disconnected during operation, as contact bounce will likely occur and cause a crash.

 

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