Interfaces and Signals > Laser > LaserGate, LaserA, LaserB

All three outputs can operate in opto-insulated 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 optocouplers take their supply from internal VCC, which causes to eliminate the opto insulation. 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-2 as shown in figures 13, 17 and 18.

laser_sj_ext

Figure 17: Laser signal optocoupler external supply

laser_sj_int

Figure 18: Laser signal optocoupler internal supply (default)

The polarity of the LaserGate, LaserA and LaserB outputs is selected via software settings.

	During USC-2 startup and when the laser signals are disabled by software, the LaserGate, LaserA and LaserB 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 19: YAG laser control signals (active low)

The maximum output frequency for the LaserA and LaserB is 2 MHz, the period resolution is about 80 ns. The minimum output pulse width for LaserA and LaserB 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).