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USC-3 Manual > Interfaces and Signals > Digital I/Os

Digital I/Os 		Previous pageReturn to chapter overviewNext page

The USC card has 10 TTL digital inputs Digi_In_0..9 and 10 TTL digital outputs Digi_Out_0..9 on the Extension - 40 pin connector.

Unlike the Opto I/Os, Laser_Gate, Laser_A and Laser_B the Digi I/Os are not optically isolated from the USC main power circuit.

 

Digi_In input levels:

•The voltage on Digi_In_0..9 may not exceed +24 V in respect to GND.

•The input level of Digi_In signals in respect to GND:

olow: between 0 V and UTh - 1 V

ohigh: between UTh + 1 V and 24 V

▪By default, the input threshold for activation of the Digi_Ins UTh is around 2.0 V. This threshold can be increased by the use of an appropriate resistor RExt must be added. Calculate the value of the resistor with the following formula:

 

Digi_Out output levels:

•The output levels and max. currents are listed in chapter Electrical Characteristics.

warning

During USC-3 startup and when the laser signals are disabled by software, the Digi_Outs will go into tri-state. It must be assured that the connected device defaults to a safe operation in this case. Potentially, a pull-up or pull-down resistor (about 4k7 ohm) has to be added to put the connected device into a safe state.