1-21. ELECTRONIC STATION (cont)
(3) Programmer CCAs The four programmer CCAs are plugged into the backplane and
receive digital input signals in the form of hexadecimal data bytes.
Since the cir-
cuitry in the four programmer CCAs are identical, the following description applies to
A total of nine data bytes, plus a data transfer strobe following each byte,
constitutes a complete instruction sequence.
(a) The first three data lines and the address select switches are monitored
by the card address detector.
If the content of the three data lines and the switch
positions coincide, the card address is correct and the MCA signal is applied to the
If the subsequent incoming signal is identified as the ASCII character
"=" on its separate line, the control circuit enables the transfer of the next seven
data bytes, as well as a shift and a latch signal, across the opto-isolators.
(b) The data bytes are now entered into the shift registers by means of the
shift command, which enables the shift registers until all seven data bytes are
Following the last data byte, the latch command strobes the parallel data
into the latches.
The data bytes representing the channel A and channel B fields are
applied to the digital to analog converters (DAC-A, DAC-B), while the range and
polarity byte is transferred to the control circuits within the programmable ampli-
fiers to establish the amplifier polarity and output ranges. Channel A supplies O to
± 10 volts, with reference to analog common, and
with reference to analog common, to programmable
d. PROGRAMMABLE POWER SUPPLY ASSEMBLY 1A3
The programmable power supply
Channel-B supplies O to ± 1 volt,
power supply assembly 1A3.
assembly 1A3 (FO-5) consists of four
power supplies (PS1-PS4). PS1 and PS2 are adjustable form O-36 vdc output. PS3 and
PS4 are adjustable from O-75 vdc output.
Refer to FO-9 for dc power distribution
Circuits of the four power supplies are identical, therefore the following
description applies to all.
The power supply is basically a voltage and current sta-
bilized dc source with a sharp crossover between the voltage and current mode of oper-
A linear series pass element is controlled by either the current control chan-
nel or the voltage control channel.
The operating mode is determined by the value of
the front panel adjusted (or externally controlled) output voltage and output current,
and by the magnitude of the load resistance.
(2) Voltage Mode.
In the voltage mode of operation, the voltage comparator
amplifier senses any change in the output voltage by comparing it to a reference
potential, developed by the voltage control amplifier. When a change is detected, an
error signal is amplified and becomes a control signal for the driver stage.
control signal is applied, via the driver stage, to the pass element which increases
or decreases its conductance in response to the driver signal as required to maintain
the output voltage at the desired value.