DUPLEX MODE. —The duplex mode is the
primary control mode for the KCMX. Either of two
computers may have control of the KCMX at one time.
Each computer must request control by means of an
external function. Once the desired mode selections
and data exchanges have taken place, the controlling
computer must place the KCMX in a neutral state
through the use of a release local external function.
RECEIVE DATA FROM UNIT COMPUTER
(RDUC) MODE. —To output data to the KCMX, the
controlling computer must place the KCMX in the
RDUC mode by external function. In the RDUC mode,
the KCMX is capable of receiving data consisting of
DOC output words or control words. DOC data and
control signals are the only KCMX functions used to
transmit information to external subsystems or
equipment.
TRANSMIT DATA TO UNIT COMPUTER
(TDUC) MODE. —The TDUC mode is used to input
addressed data to the controlling computer. The
computer places the KCMX in TDUC mode. The
external function command specifies the address or
addresses of the data to be transmitted to the computer.
TDUC AND RDUC MODE. —The KCMX can be
placed in the TDUC and the RDUC modes at the same
time. Both modes will operate simultaneously under
the control of one computer.
INTERRUPT MODE. —The KCMX operates in
the interrupt mode when indicating an abnormal
condition (Type I interrupt) or upon receipt of
high-priority data from DDI addresses or DIC external
functions or interrupts (Type II interrupt).
KEYSET ERROR MODE. —The computer
places the KCMX in the keyset error mode to send an
error signal to the addressed keyset.
Demand Digital (DD) Inputs
The 16 demand digital (DD) inputs (figure 13-11)
use 30-bit words. Eight DD devices are daisy chained
on each of two cables. Each DD device (keyset) is
controlled by three control signals: enter, read, and
error. A total of 24 control signals is required for the
eight DD devices on an input cable.
The eight DD devices on the first cable are called
group 1 and are assigned KCMX addresses 1 through
10 (all KCMX addresses are octal). Group 2 consists
of the other eight devices on the second cable and are
referenced by KCMX addresses 11 through 20. Group
1 DD devices may function in either a data (DD) mode
or an interrupt (DDI) mode. Group 2 devices function
only in the data mode.
ERROR SIGNAL. —The error signal is activated
by the KCMX under computer control and is a
program-controlled function. It is normally generated
in response to a format error in the operator entered data.
The signal lights the error indicator on the DD device.
ENTER SIGNAL. —The enter signal is generated
by the DD device when it has a data entry input ready
for transmission to the controlling computer. The
KCMX, when requested by the controlling computer,
samples (reads) the data on the data lines from the DD
device.
READ SIGNAL. —The read signal is used to
activate the DD device data lines. The KCMX activates
the read signal for the addressed DD device and waits
200 msec before sampling the data. When the DD de-
vice receives the read signal, the data lines back to the
KCMX are activated. The KCMX waits the 200 µsec,
samples the data, and inputs the data to the controlling
computer.
DEMAND DIGITAL INTERRUPT (DDI)
INPUT. —A demand digital interrupt (DDI) is nothing
more than a demand digital device assigned to group 1
when that group is in the interrupt mode. Group 1 is
placed in the interrupt mode by a computer external
function command. The enter signal is processed
differently in the interrupt mode. The KCMX
automatically tests and honors the DDI enter signals
through an interrupt priority sequence. The KCMX
reads the entered data and inputs it to the controlling
computer as an interrupt code rather than as a data input
word. There is no delay in waiting for the computer to
request a data input (DD mode).
READY DIGITAL (RD) INPUTS. —There are up
to eight inputs for ready digital data (figure 13-11);
KCMX addresses 63 through 71 are used for 12-bit data
while address 72 is used for 30-bit words. This data is
obtained from synchromechanical devices such as the
radar azimuth converters (RACs). The data normally
represents a digitized analog antenna position.
The eight ready digital (RD) inputs occupy separate
cables and use only one control signal (enter signal)
each. These eight separate signals inform the KCMX
that the data on the line is valid and can be sampled.
The data is sampled by the KCMX when the
corresponding address is designated by the controlling
computer to be interrogated and have the data entered
(TDUC). If the KCMX attempts to sample the data
lines and the enter signal is temporarily false, the
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