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2-12
Functional Description
Burst Mode Conversion Clock
In burst mode and burst mode with SSH, the burst mode conversion clock
determines the conversion rate, while the pacer clock determines the rate
at which bursts occur. In this manual, the conversion rate during burst
mode conversion is referred to as the
burst mode conversion rate
, and the
rate at which bursts occur is referred to as the
scan rate
.
DAS-1800 Series software utilities allow you to program the pacer clock
to adjust the interval between burst mode scans. This software also allows
you to adjust the burst mode conversion rate. The burst mode conversion
clock frequency is programmable for a range of 15.625Hz to 333kHz.
Without SSH hardware attached to the DAS-1800HC Series board, the
sample rate (pacer clock rate) should be set for no more than the burst
mode conversion clock rate divided by the number of channels in the
burst. The maximum burst mode conversion clock rate is gain-sensitive,
as explained in “Maximum Achievable Throughput Rates” on page 2-5.
With SSH hardware attached to the DAS-1800HC Series board, the
sample rate (pacer clock rate) can be no more than the burst mode
conversion rate divided by the sum of one plus the number of channels in
the burst. For information on the signal interface between a DAS-1800HC
Series board and SSH hardware, refer to “Using Digital Control Signal
SSHO” on page 2-20.
Triggers
A trigger starts an analog input operation. The polarity of external triggers
in the DAS-1800HC Series boards is software-selectable. You can use one
of the following trigger sources to start an analog input operation:
●
Internal
— When you enable the analog input operation, conversions
begin immediately.
●
External Analog
— While an analog trigger is not a hardware
function of the DAS-1800HC Series boards, you can program an
analog trigger using one of the analog input channels as the trigger
channel. The DAS-1800HC Series DriverLINX software provides
functions for an analog trigger; refer to “DriverLINX Configuration
Notes” on page C-1 and the DriverLINX on-line documentation
provided with the DAS-1800HC Series board.
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