PCI-1718 Series User Manual 24
3.2.5 Timer Clock Selection (JP8)PCI-1718’s JP8 controls the input clock frequency for the 8254 program-
mable clock/timer. You have two choices: 10 or 1 MHz. This lets you
generate pacer output frequencies from 2.5 MHz to 0.00023 Hz (71 min-
utes/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 1 and Div2 are the
dividers set in counter 1 and counter 2 in the 8254.
Table 3.5: Summary of Jumper JP8 Settings
Jumper Function description
JP8 1 MHz (default)
10 MHz