User manual

PCL-818 Series User Manual 26
Internal Voltage Reference, -10 V or -5 V (JP10)
If you use an internal reference voltage (set with JP11), the PCL-818HD/
HG/L provides a choice of DC internal reference voltage sources: -5 V
and -10 V.
Table 3-4: Jumper JP10 Settings
Timer Clock Selection (JP8)
The PCL-818HD/HG/L’s JP8 controls the input clock frequency for the
8254 programmable clock/timer. You have two choices: 10 MHz and 1
MHz. This lets you generate pacer output frequencies from 2.5 MHz to
0.00023 Hz (71 minutes/pulse).
The following equation gives the pacer rate:
Pacer rate = Fclk / (Divl * Div2)
Fclk is 1 MHz or 10 MHz, as set by jumper JP8. Div l and Div2 are the
dividers set in counter 1 and counter 2 in the 8254. See Chapter 8 for
more details.
Table 3-5: Jumper JP8 Settings
Jumpers Function Description
JP10 5 V (default)
10 V
Jumpers Function Description
JP8 1 MHz (default)
10 MHz