2-20
Functional Description
Figure 2-7. Timing for the Generation of TGOUT
Using Digital Control Signal SSHO
The SSHO digital control signal is normally generated by DAS-1800HC
Series boards to accommodate an SSH hardware interface. The SSHO
signal is generated by either the onboard counter/timer clock or a
user-supplied external clock. Characteristics of the SSHO signal when
used for SSHO 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 an active edge
of the pacer clock and remains there until 200ns after the ADC starts
conversion of the last channel in the burst.
●
SSHO remains low until another active edge of the pacer clock. To
ensure adequate sample time for the SSH hardware, the pacer clock
period should be as follows:
Pacer Clock Period
≥
(Number of Ch 1)
×
(Burst Period)
software enables
conversions
software disables
conversions
< 1µs
c. Internal Trigger/Gate
200ns typical
b. TGIN as a Gate
200ns typical
a. TGIN as a Trigger
remains active until
conversions are
disabled by software
TGOUT
TGIN
TGOUT
TGIN
TGOUT
Internal
Trigger/Gate
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