Counter Time Base

Establishes a hardware time-base for the model using one of the two 32-bit general purpose counters on the Q8 data acquisition system.

Library

qctools

Description

The Counter Time Base block for the Q8 series of I/O cards provides a mechanism for using one of the hardware counters on an installed Q8 card as a time-base for the real-time code. This block is used in Windows to achieve sampling rates faster than 10kHz or to synchronize multiple computers. To synchronize multiple computers, use a Counter Time Base block on the "master" with the "Enable external output" option checked and use an External Time Base block on all the "slaves". Connect the CNTR_OUT or WATCHDOG output (according to the Counter Time Base clock source) of the master to the EXT_INT lines of the slaves.

	Note that Time Base blocks may only be used in Windows if the Q8 Windows driver has been converted to an RTX driver using Convert To RTX in the RTX Properties control panel.

Parameters and Dialog Box

Board Number

The board number of the I/O card. If there is only one Q8 board in your system, then the board number should be zero. The second Q8 board in your system is board number 1, etc.

Clock Source

The counter to use as the time-base. The real-time code will be driven by interrupts generated by the counter. There are two 32-bit general purpose counters available on the card: COUNTER and WATCHDOG. The period of the counter is determined by the Fixed Step Size parameter in the Simulation Parameters dialog. The period may range from 60 ns to 257 seconds (4.3 minutes), in 60 ns units, although the current generation of personal computers is not capable of 60ns sampling periods.

CNTR_EN Polarity

Polarity of the CNTR_EN input. If this option is not checked then the CNTR_EN is an active-low input. Otherwise it is active-high. The CNTR_EN line has a pullup resistor to bring it high when the input is unconnected. Hence, this option is normally checked to enable the counter by default.

Output Latency

If the Output Latency box is checked, then the block will have a scalar output port that produces the latency between generation of the interrupt and execution of the block. Otherwise the block has no output. The Time Base blocks have a default block priority setting of 100 so that the code for the block is executed first in the generated code.

Enable External Output

When this option is checked, the square wave counter output will appear on the external counter output pin on the CONTROL header of the Q8 terminal board. For the COUNTER clock source, the output pin will be the CNTR_OUT pin. For the WATCHDOG clock source, the output pin will be the WATCHDOG pin.