BINARY-CODED WORD INTERFACE. The
control signals in the ICCG interface are primarily in a
binary-coded word format. The binary words are shifted
into and out of the crew ICS panels, the IRC panel, and
the SLU on pairs of multiplex lines. The crew ICS panels
and the IRC have unique binary word addresses that are
identified by a roll call sequence performed in the SLU.
Every 25 milliseconds, each crew panel and the IRC are
interrogated for a change-of-status by the SLU. This
change-of-status data is stored in the SLU until it is
transferred to the general-purpose digital computer
(GPDC) for permanent storage. The GPDC will be
discussed in a later chapter of this TRAMAN. The
change-of-status data is then processed by the SLU to
produce mode forcing signals that are sent to the
appropriate peripheral and ICCG components.
HARD-WIRE SIGNAL INTERFACE. The
volume control signals and backup mode control and
status signals are interfaced by separate lines between
the components. These signals are analog voltages and
ground circuits. These signals produce changes in the
components as the controls are adjusted or pressed
without being processed first.
Most of the indicators in the ICCG are either mode
or function status indicators that come on amber and
green. When the indicator comes on green, it means that
the corresponding function is available for selection.
When that function is selected, the indicator will turn to
amber. With the indicator off, that function is not
available for selection.
On the IRC, the IFPM indicators will illuminate
when a fault is detected in the corresponding
component. The S indicators on the crew panels will
illuminate red when the secure mode of operation is
selected for that particular radio system. The indicators
in the frequency selection section of the IRC come on
red when frequency selection is available.
Encoded and Decoded Word Format
All the components in the ICCG, except for the three
LS-602/AI panels, have identical binary encoding and
decoding circuits. The encoding circuits transform a
signal function into a binary word in the Manchester
format for transmission to another component. The
decoding circuits transform the Manchester signal
functions from another component into basic signal
functions for application to processing and control
circuits within that component.
Each of the components in the ICCG, except the
LS-602/AI, have a unique binary word address. The
component responds to an interrogation by the SLU only
when its specific address is recognized. The addresses
are incorporated into the 36-bit ICCG word format.
Each bit is a status or control function, or a part of the
5-bit component address that has a permanently
assigned slot in the 36-bit format.
The 36-bit words are serially generated and serially
transmitted binary bit words. Each bit is either a 1 or a
0. A logic 1 corresponds to a voltage level between 5.0
and 8.5 volts dc. A logic 0 corresponds to a voltage level
between -0.5 and 1.5 volts dc.
ENCODED WORD FORMAT. Encoded word
format is setup for 36-bits that are either status/control
function information or component addresses. Bit 1 is
the control bit and is always a 1.
Bits 2 through 6 are the address bits. Each com-
ponent has its own unique binary configuration. One
example of this is that the SLU recognizes the binary
number 01010 as the pilot crew ICS panel. Should this
configuration show up in bits 2 through 6, then the SLU
will process on the command data from the pilot ICS
panel during the 36-bit word cycle. Each component
address word is designated by the decimal equivalent to
its binary value. With the above example, the pilot ICS
panel address 01010 is equal to decimal 10. Therefore,
the pilot ICS panel designation is word 10.
Bit 7 is the tag bit needed for binary word house-
keeping. It is always 0 for encoded words.
Bit 8 is the enter bit for binary housekeeping. In the
encoded words it is always 1.
Bits 9 through 34 are the command functions, status,
or spare bits. Bit 35 is a command function, status, spare,
or set-zero housekeeping bit.
Bit 36 is the parity bit used for self-check in the
binary circuitry. This system uses the odd parity check.
If there are an even number of 1s in the first 35 bits, bit
36 will be a 1. If the total number of 1s in the first 35
bits is odd, bit 36 will be a 0. When a component receives
the 36-bit encoded word, its decoder checks the parity
by counting the 1s. If it comes up with an even number
of 1s, the word is not processed and a BITE indicator
is illuminated on the component that transmitted the
faulty data word.
DECODED WORD FORMAT. The decoded
word format is similar to the encoded word format with
just a few differences. Bit 1, bits 9 through 34, bit 35 and
bit 36 are the same as in the encoded word. Bits 2