National Instruments PCI-1200 Manual De Usuario

© National Instruments Corporation

timing, or you can use the three external timing signals, EXTCONV*, 
EXTTRIG, and EXTUPDATE*, for DAQ and DAC timing.

The second group of counter/timers is called group B and includes B0, B1, 
and B2. You can use counters B0 and B1 for internal DAQ and DAC 
timing, or you can use the external timing signal CLKB1 for analog input 
timing. If you are not using counters B0 and B1 for internal timing, you can 
use these counters as general purpose counter/timers. Counter B2 is 
reserved for external use as a general purpose counter/timer.

For a more detailed description of counter group A and 
counters B0 and B1, refer to the 

 and 

 sections.

The PCI-1200 has eight channels of analog input with 
software-programmable gain and 12-bit A/D conversion. The PCI-1200 
also contains DAQ timing circuitry for automatic timing of multiple A/D 
conversions and includes advanced options such as external triggering, 
gating, and clocking. Figure 4-4 shows a block diagram of the analog input 
circuitry.

Figure 4-4.  Analog Input Circuitry

Sample-
and-Hold
Amp

DAQ

Timing

Gain Select/

Mux Counter

+

Program-
mable
Gain Amp

–

ADC

A/D

FIFO

External Trigger

Counter/Timer
Signals

WRT/RD

CONV
AVAIL

A/D
RD

EXTCONV*

OUTB1

EXTTRIG

ACH0
ACH1
ACH2
ACH3
ACH4
ACH5
ACH6
ACH7

12

12

8

6

A/D

Data

Data

Data

GAIN0

GAIN1

GAIN2

Convert

Mux

ACH1
ACH3
ACH5
ACH7

AISENSE/

AIGND

External Convert

External Scan Interval

Dither
Circuitry

Dither Enable

Dither

PCI Bus

Digital

Control

Logic

MITE

PCI

Interface

Chip

Data/Address

Interface Control

Error Reporting

Arbitration

System

Interrupt

1

2

2

2

6

37

Address

Data

Control

Interrupt

1

DRQ

1

4

8

5

I/O Connector

Mux