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2-26
Functional Description
Using Digital Control Signal SSHO
The SSHO digital control signal is normally generated by DAS-1800ST
Series boards to accommodate external SSH hardware. The SSHO signal
is initiated by either the onboard internal pacer clock or an external pacer
clock. Characteristics of the SSHO signal when used for SSH hardware
control are as follows:
●
SSHO is normally low, signifying that the SSH hardware is in sample
mode.
●
SSHO goes high (into the hold mode) about 50ns after a pacer clock
pulse.
●
A/D conversion begins one burst period after the pacer clock pulse.
●
SSHO remains high until 200ns after the ADC starts conversion of
the last channel in the burst.
●
SSHO goes low and remains low until another pacer clock pulse.
To ensure adequate sample time for the SSH hardware, the pacer clock
period should be set as follows:
Pacer Clock Period
≥
(Number of Ch 1)
×
(Burst Period)
When you are not using the SSHO signal for SSH hardware control, you
can use it as a converter clock output signal. SSHO is active only during
A/D conversions. The timing for SSHO generation when the
DAS-1800ST/HR Series boards are not used for control of SSH hardware
is shown in Figure 2-10.
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