Measurement Computing USB-4301 - Manual (Page 18)

USB-4301 User's Guide Functional Details
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 Not recycle
The counter will count from 10,000 to 0, and then start at 5,000 and count to 0, then stop. If you select an edge
gating option, and Recycle mode is active, the counter only resumes counting after TC when a new active gate
edge is received.
BCD/Binary mode
Most applications use the binary mode of counting. Binary mode causes the counter to always increment or
decrement by a value of 1. The counter can have a value from 0 to 65,535.
With binary mode, a 4-bit binary number is represented by the 16 decimal numbers 0 to 15: 0 = 0b0000, 1 =
0b0001,…, 9 = 0b1001, 10 = 0b1010,…, 15 = 0b1111. (0b is used to denote binary numbers). For the numbers
0-9, there are four binary bits to represent one decimal digit, and from 10-15, there are four binary bits to
represent two decimal digits.
However, in some applications, it is useful to maintain the four-bit-to-one-digit correspondence, so the numbers
0-9 remain the same, but 10-15 and up to 99 are represented by eight bits—four for each digit. The numbers
100-999 are represented by 12 bits, and 1000-9999 are represented by 16 bits. This makes it easy to decode long
binary numbers.
For example, 0b1001 0001 0000 1001 equals 9109 in BCD (Binary Coded Decimal) mode, and equals 37,129
in binary mode. In BCD mode, the counter can only contain values from 0 to 9999 instead of 0 to 65,535 as in
binary counting.
The "Special" gate
When you enable the Special gate option and specify gating, the gate can function as a hardware re-trigger of
the counting operation. When an active gate edge is received, the counter is reloaded from the Load register and
begins counting, even if the counter is already counting when the gate edge is received.
When you enable the Special gate option and disable gating, the Gate pin associated with the counter being
configured can select the reload source for the counter. This requires the counter be in Load and Hold reload
mode. If the gate pin is low, the counter is reloaded from the Load register. If the gate pin is high, the counter is
reloaded from the Hold register.
Output control
You can configure the output pin associated with a counter to behave in five ways:

Inactive with high impedance to ground.
 Inactive with low impedance to ground.
 Generate an active high pulse when the associated counter reaches TC.
 Generate an active low pulse when the associated counter reaches TC.
 Toggle its value every time the counter reaches TC.