ADLINK DAQe-2006 - Manual (Page 83)

Operation Theory 71
EXTDTRIG and EXTWFTRIG
EXTDTRIG and EXTWFTRIG are dedicated digital trigger input
signals for A/D and D/A operations respectively. Refer to sec-
tion 4.5 for details.
EXTTIMEBASE
When the applications needs specific sampling frequency or
update rate that the card could not generate from its internal
TIMEBASE — the 40 MHz clock — you could utilize the EXT-
TIMEBASE with internal counters to achieve the specific timing
intervals for both A/D and D/A operations. Note that once you
choose the TIMEBASE source, both A/D and D/A operations
will be affected because A/D and D/A operations share the
same TIMEBASE.
AFI[0]
Alternatively, you can also directly apply an external A/D con-
version signal to replace the internal ADCONV signal. This is
another way to achieve customized sampling frequencies. The
external ADCONV signal can only be inputted from the AFI[0].
As section 4.1 describes, the SI_counter triggers the genera-
tion of the A/D conversion signal, ADCONV, but when using
the AFI[0] to replace the internal ADCONV signal, the
SI_counter and the internally generated SCAN_START is not
effective. By controlling the ADCONV externally, you can sam-
Multi-
function
input
AFI[0]
(Dual functions)
Replace the
internal
ADCONV
1. TTL-compatible
2. Minimum pulse width = 20ns
3. Rising–edge sensitive only
Replace the
internal
SCAN_START
1. TTL-compatible
2. Minimum Pulse width > 2/
TIMEBASE
AFI[1]
Replace the
internal DAWR
1. TTL-compatible
2. Minimum pulse width = 20ns
3.Rising–edge sensitive only
Category Timing signal Functionality Constraints
Table 4-9: Auxiliary Function Input Signals and Functionalities