ADLINK USB-2401 - Manual (Page 48)

38 Operation
3.6.2 General Purpose Timer/Counter
The USB-2401 is equipped with one general purpose timer/coun-
ter featuring:
X Count up/down controllable by hardware or software
X Programmable counter clock source (internal clock up to
80MHz, external clock up to 10 MHz)
X
Programmable gate selection (hardware or software con-
trol)
X
Programmable input and output signal polarities (high active
or low active)
X Initial Count loaded from a software API
X Current count value readable by software without affecting
circuit operation.
Table 3-4: Timer/Counter Pin Definition
The timer/counter has three inputs that can be controlled via
hardware or software, clock input (GPTC_CLK), gate input
(GPTC_GATE), and up/down control input (GPTC_UD). The
GPTC_CLK input provides a clock source input to the timer/coun-
ter. Active edges on the GPTC_CLK input increment or decrement
the counter. The GPTC_UD input directs the counter to count up
or down (high: count up; low: count down), while the GPTC_GATE
input is a control signal acting as a counter enable or counter trig-
ger signal in different applications. The GPTC_OUT then gener-
ates a pulse signal based on the timer/counter mode set.
All input/output signal polarities can be programmed by software
application. For brevity, all GPTC_CLK, GPTC_GATE, and
GPTC_OUT in the following illustrations are assumed to be active
high or rising-edge triggered.
Pin Function Pin Function
20 GPTC_OUT0 (GPO0) 40 GPTC_OUT1 (GPO1)
19 GPTC_UD (GPI1) 39 GPTC_AUX (GPI3)
18 GPTC_CLK (GPI0) 38 GPTC_GATE (GPI2)
17 NC 37 DGND