2-24
Functional Description
10k
Ω
pull-up resistors to +5V; therefore, the inputs appear high (logic 1)
with no signal connected.
Using Digital Control Signal DOSTB
DAS-1800ST/HR Series boards provide a strobe signal DOSTB (pin 19
of the main I/O connector or pin 37 of STA-1800U connectors J1 and J2)
for the purpose of strobing data through the digital outputs and latching
the data into a register in external equipment. Where DAS-1800ST/HR
Series boards use the positive edge of the strobe to strobe data out, you
must use the negative edge to strobe data into other equipment because
the negative edge gives you a 300ns lag to allow for delays. Data is valid
until the next strobe, as shown in Figure 2-8.
Figure 2-8. Timing Relationship between Data from DO0 to DO3 and
Latch Strobe DOSTB
Using Digital Control Signal TGOUT
When using the onboard internal pacer clock, you can use the trigger/gate
output signal TGOUT (pin 20 of the main I/O connector or pin 39 of
STA-1800U connectors J1 and J2) to synchronize other DAS-1800 Series
boards or to trigger or gate user-specific events as follows:
●
When using digital control signal TGIN as a trigger, TGOUT behaves
as shown in Figure 2-9a. Note that when you use this option, TGOUT
does not retrigger and thus cannot be used with about-trigger
acquisitions. Note also that there is a delay of about 200ns between
the active edge of TGIN and the starting edge of TGOUT.
300ns Strobe
Strobe
DOSTB
DO[3:0] Data
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