ADLINK PXI-2208 - Manual (Page 92)

80 Operation Theory
Auxiliary Function Inputs (AFI)
You can use the AFI in applications that take advantage of exter-
nal circuitry to directly control the DAQ-/DAQe-/PXI-2204/2205/
2206/2208 card. The AFI includes two categories of timing signals:
one group is the dedicated input, and the other is the multi-func-
tion input. Table 4-9 illustrates this categorization.
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
Category Timing signal Functionality Constraints
Dedi-
cated
input
EXTTIMEBASE
Replace the
internal TIME-
BASE
• TTL-compatible
• 1 MHz to 40 MHz
• Affects on both A/D and D/A
operations.
EXTDTRIG
External digital
trigger input for
A/D operation
• TTL-compatible
• Minimum pulse width = 20ns
• Rising edge or falling edge
EXTWFTRG
External digital
trigger input for
D/A operation
• TTL-compatible
• Minimum pulse width = 20ns
• Rising edge or falling edge
Multi-
function
input
AFI[0]
(Dual-functions)
Replace the
internal
ADCONV
• TTL-compatible
• Minimum pulse width = 20ns
• Rising–edge sensitive only
Replace the
internal
SCAN_START
• TTL-compatible
• Minimum Pulse width > 2/
TIMEBASE
AFI[1]
Replace the
internal DAWR
• TTL-compatible
• Minimum pulse width = 20ns
• Rising–edge sensitive only
Table 4-9: Auxiliary Function Input Signals and Functionalities