Clocks :: Quanser HIL C API

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Table of Contents > QUARC > User's Guide > QUARC External Interfaces > C Functions > Hardware > HIL API > Getting Started with the HIL C API

Clocks

The buffered I/O and task functions all have a clock parameter. The clock parameter determines the source of the timing for these functions. Clocks come in two major categories: system clocks and hardware clocks.

System clocks are provided by the operating system. System clocks, in general, may be used by more than one HIL block at the same time. In Windows, only one system clock is supported:

SYSTEM_CLOCK_1: A system clock supporting rates up to 1 kHz.

Under RTSS, three system clocks are supported:

SYSTEM_CLOCK_1: A system clock supporting rates up to 1 kHz.
SYSTEM_CLOCK_2: A system clock supporting rates up to the HAL timer period (10 kHz limit)
SYSTEM_CLOCK_3: A system clock supporting rates up to the HAL timer period (10 kHz limit)

Hardware clocks are provided by the HIL board. Hardware clocks, in general, may be used by only one HIL function at the same time. This exclusion is particularly true of task functions. Two buffered I/O functions may share a hardware clock because they do not use the clock at the same time. The number of hardware clocks available depends on the HIL board selected. For the Q8 card, for example, two hardware clocks are available: HARDWARE_CLOCK_0 and HARDWARE_CLOCK_1. The range of sampling frequencies supported by a hardware clock also depends on the HIL board selected. The Q8 card's hardware clocks have a 60 ns resolution so fast sampling rates are supported, limited only by speed of the CPU and the hardware configuration of the computer.

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