1-24. TEST CONSOLE TEST BENCH 2A2 (cont)
(3) Backplane CCAs
(a) Simultaneous Sample and Hold CCA.
The simultaneous sample and hold CCA
contains four sample and hold amplifiers together with the necessary digital control
and analog multiplexing circuitry required for operating and interrogating the sample
and hold circuits.
The sample and hold channels acquire analog signals and simulta-
neously hold them for processing.
Channels are then scanned by high-speed, multi-
plexing techniques and the resulting data represents the analog signal in digital
(b) Multiplexer CCA.
The multiplexer CCA transfers 16 differential channels
of input signals under program control.
Each channel is independently protected
against applied overvoltages.
(c) Isoplexer CCA.
The isoplexer CCA isolates each of four input signals
from common mode voltages and multiplexes the isolated differential outputs to the
analog bus under system program control.
(d) Self-test CCA.
The self-test CCA provides measurement of system power
supplies and A/D converter accuracy and settling time, under control of the computer
(e) Expansion CCAs.
The expansion CCAs serve to select the correct chassis
(master or expansion) for analog and digital transactions. Since there is no
expansion chassis used, the master chassis is selected.
The expansion CCAs transmit
the analog signals even, odd, and signal return to the signal processor CCA and
then to the A/D converter CCA.
The digital section of the expansion CCAs receives
bits Al thru All of the 12-bit analog address word, generated from the address
register on the front panel.
A12, the least significant bit of the analog address
word, goes only to the signal processor CCA where it is used in channel selection
during single-ended operation.