Position compare pulses

We wish to clock our scan pixels to motor drive steps on the XPS. The XPS offers the feature to send out pulses at well defined positions. These pulses have a width of 200ns with a maximum frequency of 2.5MHz and a latency of at most 50ns. The trigger resolution with AquadB encoders, that all our stages have, is equal to the encoder resolution. By default we use this maximum resolution and let the clock divider on the clock interface board pass only one pulse per pixel. Unlike with the old MM-3000 controllers, we could have the XPS send out only 1 pulse per pixel for variable pixel size. But since we still need the clock divider for SGM pulses, we chose not to do this.

The mating connector for the position compare output is a LEMO FGG.0B.306.CLAD52. The signals go into a DB-9 connector on the clock interface board. The pin assignment is listed in Tab. 11.4 and shown graphically for the LEMO in Fig. 11.1. The signals are open collector type and accept up to 30V and 40mA. The 5V output can supply a max of 50mA. In an external (DB-9) adapter between the XPS controller and the clock interface we connect the 5V over a 470$\Omega$ resistor each to both of the pulse lines. This way we pull up the signals to +5V and roughly 10mA to ensure fast transitions.

Table 11.4: Connections to see the postion compare pulses on the Newport XPS-C8 motor controller/driver unit. The position enable signal is low, when the position compare is active. We don't use those, since we have position compare activated over the whole travel range.

LEMO pin #	Function	DB-9 pin #	Newport cable	custom cable
1	+5V	1	Red
2	Pulse enable 1	NC	White
3	Pulse 1	3	Blue
4	Pulse 2	5	Green	Orange
5	Pulse enable 2	NC	Yellow	Green
6	Ground	2	Black

Figure 11.1: Pin assignment of LEMO FGG.0B.306.CLAD52. The left side is looking into the female connector on the backside of the XPS. The right side is looking into the mating male connector on the cable.