National Instruments DIO 6533 - Manual (Page 61)

Chapter 5 Signal Timing
DIO 6533 User Manual 5-2 © National Instruments Corporation
Request Timing
Internal Requests
Figure 5-2 shows internal request timing. You can select a timebase and
an interval. The request pulses low once per data transfer. The duration
of the low pulse is equal to one timebase. The period of the request
pulse is equal to the interval multiplied by the timebase (in LabVIEW,
you specify an overall period, and the software selects the interval and
timebase).
Figure 5-2. Internal Request Timing
External Requests
Figure 5-3 shows external request timing. The request signal must pulse
low and return high. The request pulse low and high durations must be
at least 20 ns each. The minimum period is 50 ns.
Parameter Description
t
c
Cycle time
t
lw
Width of low pulse
t
p
Propagation time to valid output data
t
su
Setup time
t
h
Hold time
Data (Output Mode)
Data (Input Mode)
REQ
th tsu
30 ns
Min
0 ns
Min
tp
30 ns
Max
tlw
Programmable = One Timebase
tc
Programmable = Interval x Timebase