Interfaces and Signals > Laser > Laser_Gate, Laser_A, Laser

All three outputs can operate in opto-isolated mode. For this the EXT_LASER_VCC (pin 11) and EXT_LASER_GND (pin 30) must provide the supply. EXT_LASER_VCC may not exceed +5 V in respect to EXT_LASER_GND.

As default the opto couplers take their supply from internal VCC, which causes to eliminate the opto-isolation. In this case the voltage of all 3 outputs are TTL compatible in respect to GND. The mode can be selected by solder jumpers on the bottom side of the USC-3 as shown in figures 16 and 17.

laser_sj_ext

Figure 16: Laser signal opto coupler external supply

laser_sj_int

Figure 17: Laser signal opto coupler internal supply (default)

The polarity of the Laser_Gate, Laser_A and Laser_B outputs is selected via software settings. Default is active low.

	During USC-3 startup and when the laser signals are disabled by software, the Laser_Gate, Laser_A and Laser_B will go into tri-state. It must be assured that the Laser 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 laser into a safe state.

For YAG style laser mode the output timing (active low mode) is as follows:

YAG style

Figure 18: YAG laser control signals (active low)

The maximum output frequency for the Laser_A and Laser_B is 4 MHz, the period resolution is about 80 ns. The minimum output pulse width for Laser_A and Laser_B is about 167 ns.

	The minimal output frequency of the laser signals is 0.190 Hz. This results from the 50 kHz reference frequency with 18 bit resolution which is used for frequencies < 381.46 Hz (= 0x20000).