ADLINK PCM-9112+ - Manual (Page 25)

Installation • 17
2.7 Clock Source Setting
The programmable interval timer 8254 is used in the PCI-9112. It provides 3
independent 16-bit programmable down counters. The input to counter 2 is
connected to a precision 2MHz oscillator for the internal pacer. The input of
counter 1 is cascaded from the output of counter 2. Channel 0 is free for
user applications. There are two selections for the clock source of channel 0:
the internal 2MHz clock or an external clock signal from connector CN3 pin
35. The setting for clock source is shown as Figure 2.5.
Internal Clock
Source: 2MHz
(default setting)
External Clock
Source JP2
JP2
INTCLK
EXTCLK
INTCLK
EXTCLK
Figure 2.5 Timer's Clock Source Setting
2.8 D/A Reference Voltage Setting
The D/A converter's reference voltage source can be supplied both internally
and external. The external reference voltage comes from connector CN3 pin
31 (ExtRef1) and pin12 (ExtRef2), see section 3.1. The reference source of
the D/A channel 1 and channel 2 are selected by JP4, respectively. The
possible settings are shown below: