Adlink DAQe-2006 Manual do Utilizador descarregar pdf (Página 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

1 2 ... 78 79 80 81 82 83 84 85 86 87 88 ... 91 92

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