Reset generator

The reset generator generates the SYSRESET signal and the ACFAIL signal for a VME system in accordance with the VITA standard:

The reset generator has the following functions:

1. It generates a defined reset impulse
2. It monitors the +5 V operating voltage
3. It monitors the +3.3 V operating voltage (can be disabled)
4. It monitors the mains voltage (can be disabled)
5. It provides a connection for an external reset button

Deviations of the operating voltages from the specifications of the standard may result in uncontrolled VME system operation. This may occur particularly when the system is switched on or off. The reset generator makes sure that the system is halted in such situations via the SYSRESET signal. To do this, the +5 V and +3.3 V operating voltages are monitored. In the case of +5 V only systems, the +3.3 V operating voltage monitoring function can be disabled by removing the jumper connecting pins 5 and 6 of plug connector SV2.

order to detect power supply problems early on and, if necessary, to initiate emergency measures before the operating voltage fails completely, the reset generator also monitors the mains voltage and provides the ACFAIL signal. To minimize wiring requirements, the mains voltage monitoring function is equipped with a capacitive sensor: The power cord merely needs to move past the electrode of the reset generator. Additional plugs, cables, etc., are not required. Potentiometer POT1 can be used to adapt the sensor’s sensitivity to different voltages. For DC systems, the mains voltage monitoring function can be disabled by removing the jumper connecting pins 3 and 4 of plug connector SV2.

An external reset button can be connected to pins 1 and 2 of plug connector SV2. When this button is pressed, the reset generator generates a defined SYSRESET impulse that complies with the VITA standard.