Measurement Computing USB-4302 - Manual (Page 16)

USB-4302 User's Guide Functional Details
16
Oscillator output (OSC OUT)
The oscillator output connector (pin 30) outputs a configurable clock frequency. You can select the source of
the oscillator and also select dividers for the oscillator programmatically to set the output rate.
Ground (GND)
The ground ( GND ) connector (pin 11) provides a common ground for the digital and counter I/O connections.
Oscillator output
You can set the oscillator input programmatically to one of five internal frequency sources or one of 10 external
input pins. The oscillator output can be divided by any number from 1 to 16 before being output to the OSC
OUT pin.
Internal sources
The base frequency for the internal frequency sources can be set through InstaCal to one of four different
frequencies — 1.0000 MHz, 1.6667 MHz, 3.3333 MHz, or 5.0000 MHz. This base frequency is used to
generate the five internal frequency sources — FREQ1 through FREQ5.
FREQ1 is the same as the base frequency, and each successive internal frequency following FREQ1 divides the
base frequency by another multiple of 10. For example, FREQ2 is the base frequency divided by 10, FREQ3 is
the base frequency divided by 100, and so on. This is illustrated in the following table.
Internal frequency values for different base frequencies
1.0000 MHz 1.6667 MHz 3.3333 MHz 5.0000 MHz
FREQ1 1.0000 MHz 1.6667 MHz 3.3333 MHz 5.0000 MHz
FREQ2 100.00 kHz 166.67 kHz 333.33 kHz 500.00 kHz
FREQ3 10.000 kHz 16.667 kHz 33.333 kHz 50.000 kHz
FREQ4 1.0000 kHz 1.6667 kHz 3.3333 kHz 5.0000 kHz
FREQ5 100.00 Hz 166.67 Hz 333.33 Hz 500.00 Hz
External sources
In addition to the five internal sources, the frequency source for the oscillator can be an input signal connected
to any of the five counter input pins ( CTR1IN – CTR5IN ) or any of the five gate pins ( CTR1GATE –
CTR5GATE ). The input signal can have a maximum frequency of 20 MHz on the counter input pins, and a
maximum frequency of 7 MHz on the gate pins.
The table below applies to all internal and external sources.
Oscillator sources
Source Description
CTRINPUT1 Counter 1 input pin
CTRINPUT2 Counter 2 input pin
CTRINPUT3 Counter 3 input pin
CTRINPUT4 Counter 4 input pin
CTRINPUT5 Counter 5 input pin
GATE1 Counter 1 gate pin
GATE2 Counter 2 gate pin