one-shot circuit output is directly applied to the lamp
drivers. The lamp drivers cause the LSB lamp to come
on amber and the USB lamp to come on green. Once the
switchlight is released, an enter pulse is inserted into the
word storage of the exhale word generator. If the IRC is
in the manual mode, this enter pulse will cause the
parallel transfer of the data bits from the one-shot
circuits to the word storage register. When the
switchlight is released, parallel data from the one-shot
data is inhibited from the lamp drivers. The indicators
change to the color configuration represented in the
status configuration memory. The lamps go off
momentarily because of the 25-millisecond cycle time
of the roll call sequence required for updating the status
registers. The parallel data goes from the word storage
register to the parallel-to-serial word converter, and
then, under control of the clock and roll call control, to
the exhale word inhibit AND gate. From here it is
transferred to the exhale word assembly register, where
the roll call address and tag bit are added. A parity bit is
also added if the first 35 bits are even. The clock pulse
and data are combined and then shifted out on the
The second part of the roll call 1 data is now in
Manchester format and is applied to the other
components on port 2. Only the SLU recognizes roll call
1 in its digital control section. Roll call 1 is an exhale
word with respect to the IRC, but it is an inhale word in
respect to the SLU.
The inhale word enters the SLU through the line
receiver and is transferred to the inhale word register.
Here the data and the clock pulses are separated, and the
data is shifted to the input register under the control of
the derived clock pulses. This is the only function of the
derived clock pulses. Once the data is shifted to the input
register, the master clock is used to shift the data from
one buffer to another.
The roll call word is shifted into the valid word
register. This register validates the word by ensuring that
there are 36 bits, the address is 5 bits long, the address
has a control list and a tag bit, and the word parity is odd.
If any of these conditions are not met, the word is sent
to the not-valid register. If the input word is invalid three
times, the status register sets the BITE indicator on the
component that sent the word. If the word is valid, a
valid word signal is generated, and the enter bit of the
derived data is examined. If the enter bit is not a binary
one, no further processing is done. The SLU only
processes data if a change is present on the inhale word.
If a change is present, the enter bit is a binary one.
If the inhale word is valid and it has an enter bit, it
is sent to the HF configuration buffer. Here it is loaded
into the multiplex register by the clock pulses and
unique strobe G24. The multiplex input register shifts
the data to the word decoder, where it is converted from
serial binary format to parallel binary format. This
parallel data is used to make the configuration change.
The data is also converted back to serial binary format
and stored for use in the exhale word assembly register
for the next roll call 1.
ROLL CALL 2. After the second part of roll call
1 is processed by the SLU, the first part of roll call 2 is
processed. Roll call 2 originates during word storage in
the HF conjuration buffer of the SLU. The exhale
word is sent from the SLU on the common multiplex
line. Each component on the common multiplex line
compares the address of roll call 2 with its own address.
Only the IRC recognims roll call 2.
The IRC processes the word in its digital control
section the same way as the SLU did. The derived data
is then sent to the input register where it is validated. The
input register senses that the tag bit is a binary one. The
binary one starts a 300-microsecond selective strobe
counter and a 500-microsecond exhale word counter.
The valid roll call 2 word is sent to all the display
registers in the IRC, but because of the address, only the
HF configuration status display register will receive
clock pulses. The clock pulses will shift the roll call
word into the inhale word decoder and storage register.
Here it will wait until the selective strobe pulse transfers
the parallel word to the lamp drivers. The selective
strobe pulse is sent when the 300-microsecond counter
times out, signaling the end of the inhale word time.
The lamp drivers turn on the lamps by applying aground
to the low side of the lamps. The high side of the lamps
is supplied by the lamp dimmer control circuit.
When the 500-microsecond timer times out, the IRC
exhale word is applied to the multiplex lines. This word
is the SLU inhale word, and it is processed exactly like
the inhale word for roll call 1. The SLU will ensure that
the enter bit is a binary one, and if so, will check the
frequency to see if it is a legal frequency. If the
frequency is legal, the word is processed and sent to the
HF radio set in binary-coded-decimal (BCD) format. If
the word is an illegal frequency, the frequency that is set
upon the thumbwheel switches (on the SLU face) is sent
to the HF set in BCD format. The operating frequency
status word, which is the next word to be exhaled by the
SLU, will equal the frequency that was sent to the HF
radio set. If the frequency selected on the IRC is legal,