500-003111-000
3-16
OUTPUT
BUFFERS
AND
SWITCHES
P2 I/O
CONNECTOR
OUTPUT 00
OUTPUT 01
12-bit DAC
12-bit DAC
OUTPUT
ON-LINE
INTERNAL
DATA BUS
SEL OUTPUT 00
SEL OUTPUT 01
12
VME
PORT
Figure 3.8-1. Analog Output Channels
M3111/F3.8-1
3.9 BUILT-IN-TEST
Self-test provisions in the VMIVME-3111 design permit
program-controlled verification of all active components on the board.
3.9.1 Self-Test
Multiplexers
The signal routing paths and multiplexers involved in the board-level
self-test are shown in Figure 3.7-1. The two analog outputs are connected by
the self-test multiplexers to the low channel input of any of the analog input
multiplexers. This arrangement permits any one of the analog outputs to be
sampled by the ADC. It also verifies the operation of the analog input
multiplexers by exercising them with known signal levels.
In addition to accepting the selected analog output signal, the self-test
multiplexer permits the HIGH and LOW inputs of the Programmable Gain
Amplifier (PGA) to be switched simultaneously to signal return. This feature
provides a precision "zero" signal for software-correcting common zero offsets in
the analog input channels.
Because the low channel inputs of the input multiplexers are shared
by both the analog inputs and the self-test multiplexer signal, the corresponding
input channels also are routed through the self-test multiplexer.
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