VXI VT1422A, Руководство пользователя

Страница: 99 / 529

Programming the VT1422A for Data Acquisition and Control 97 Chapter 4
Multifunction DAC?
The VT1422A is a complete data acquisition and control system on a single
VXI card. It is multifunction because it uses the Signal Conditioning
Plug-on (SCP) concept whereby analog input/output and digital input/output
channels can be mixed and matched to meet various application needs. It can
be self-contained because it has local intelligence to permit the card to run
stand-alone with very little interaction required from the supervisory
computer.
Flexible Signal
Conditioning for Input
and Output
The VT1422A has eight SCP positions with each SCP position capable of
addressing up to eight channels of input or eight channels of output for a
total of 64 channels. These 64 channels are known as the on-board channels.
The eight SCP slots can be used for any of the analog/digital SCPs available
for the VT1422A which cover most data acquisition and control needs.
Remote Multiplexing and
Signal Conditioning
In addition, each SCP slot that contains a VT1539A SCP can operate two
Remote Signal Conditioning Units (RSCUs) that externally multiplex up to
32 channels each. These channels are known as remote channels because
they are multiplexed remotely to the VT1422A. So, with 32 channels per
RSCU and 16 RSCUs, the VT1422A can make analog measurements on
512 remote channels. The upper left corner of Figure 4-1 shows how
Remote Signal Conditioning Units fit in.
Figure 4-1. Simplified Functional Block Diagram
VT1539A
Voltage
Temperature
Resistance
Strain
Sample/Hold
Digital State
Frequency
Totalize
(l
ik
e V
T
1
529A
)
Re
m
o
te
Si
g
.
Co
nd
.
U
ni
t
A
n
a
lo
g
M
u
ltip
le
x
e
r
Anal
og
In
put
S
C
P
s
A/D
Trigger Timer
Digital Signal Processor (DSP)
Trigger System
EU Conversion
Output
System
Output Buffer
(O100-O163)
Input Buffer
(I100-I163)
Global Data
Main Program
C Algorithm Code
D
igi
ta
l
Inpu
t
S
C
P
s
A24 Program/Data Memory
static float profile[ 100 ];
main()
{
if ( State_1 ) alg1();
}
alg1()
{
static float in_val, j;
in_val = I100 - 5.3;
O108 = in_val * profile[j];
writecvt( inval, 10 );
writefifo( O101 );
}
Current
Value
Table
(CVT)
FIFO
Buffer
A16
Command
Register
VXI
b
u
s
D
igi
ta
l
O
u
tpu
t
S
CP
s
An
a
log
Out
p
u
t
SCPs
Voltage
Current
Static States
Pulse per Trigger
Pulse Width Mod.
Frequency Mod.
32
Remote
Channels