TM 11-5820-890-30-4
12-13. PRIMARY CONTROL SIGNALS. Continued
The control module also checks the MODE, CHAN, and RF switch positions. The control module sets the MODE
SW COM line to Iogic 1. The control module checks the FH and FH/M lines. If neither is at logic 1, the RCU is set
for SC operation. The CHAN switch is BCD encoded as follows:
CHAN
PRESET 0
PRESET 1
PRESET 2
CUE
0
0
0
MAN
0
0
1
1
0
1
0
2
0
1
1
3
1
0
0
4
1
0
1
5
1
1
0
6
1
1
1
The control module checks the M, HI, and PA lines from the RF switch. If none are at logic 1, the RT RF output is
set for low power operation.
The keyboard display is controlled by the control module. The SERIAL DATA, DISPLAY CLOCK, DISPLAY
ENABLE-N, and DISPLAY GATE-N provide the information needed by the display drivers.
The keyboard is made up of 16 switches (keys). They are arranged in a four-by-four switch matrix. The control
module checks the X and Y lines to see if a key has been pressed. The Y lines (rows) are normally at logic 1. The
X lines (columns) are normally at logic 0. When a key is pressed, the Y line will be pulled to logic 0. The X line will
be pulled high (to about 6 V dc).
12-14. SELF-TEST.
The RCU performs an internal self-test, followed by a self-test of the remote RT (if attached), when the FCTN
switch is set to TST. See figure FO-26. OPEN is displayed when the RCU passes self-test and a remote RT is not
attached, or the remote RT is not in REM. FAIL9 is displayed when the RCU fails self-test, with or without a remote
RT attached. GOOD is displayed when both the RCU and remote RT pass self-test. FAIL numbers other than 9 are
displayed when the remote RT fails self-test and the RCU passes (see chapter 2).
When the FCTN switch is set to TST, the control module initiates self-test routines. The control module activates
the TEST line that enables built-in-test circuitry in other RCU modules. The control module also performs an
internal memory (RAM and ROM) test and activates the CONTROL XMT ENBL and CONTROL FSK DATA inputs
to the two-wire interface. The CONTROL DET-N and CONTROL RCV DATA outputs are monitored by the control
module for correct responses. in addition, the control module tells the fill routing module to enter self-test via the
asynchronous link and receives test information from the fill routing module via the link. The fill routing module
performs an internal memory (RAM and ROM) test, a test of the data rate selection circuitry, a fill routing timer
and DMA test, and a test of the fill I/O bus. The fill routing module also activates the TEST/R line which enables the
COMSEC module’s self-test. COMSEC self-test information is reported to the control module on the COMSEC
FAULT line. The TEST output of the control module enables built-in-test circuitry in the data rate adapter portion
of the ICOM control module. The data rate adapter uses the PT DGTL CLK and 192-kHz CLK outputs of the main
switching module to perform its self-test. The data rate adapter internality transmits and receives code words
during the self-test. Data rate adapter self-test information is reported to the control module on the DATA MDL
STATUS line. The bit sync network in the bit sync switching module is tested in self-test. TEST enables an 8-kHz
clock, divided down from the 640-kHz clock, into the network. The control module monitors the ACQ/TRK #1 (BS
MDL TEST) to see if the network locked onto the signal. In the main switching module, the divider network and
PTT circuits are tested. The control module monitors the MAIN SW TEST line for results.
12-20
