2-14. MlL-STD-1553B CONTROL OPERATION. Continued
The address connector permits connecting five address lines and a parity line. This determines the odd parity
and address to be looked for on the MlL-STD-1553B buses, When the EMERG-N pin is activated, the front panel
will place the rt in single channel and preset 1. If no preset is present, the f rent panel will load the emergency
frequency (40 .500 MHz) into preset 1. The ZEROIZE-N pin is used to activate the Z-A (zeroize all) function.
A reset circuit generates a negative reset pulse at power turn-on. This is used to start the microprocessor at the
correct place in its program. The reset circuit also holds the reset negative when LV RESET is present. LV RESET
is present when the +28V line drops to about +18V. LV RESET is supplied by the interface module.
Interface between the MlL-STD-1553B control panel and the rt is identical to that described for the local control
operation (para 2-12).
The fill circuit is identical to that described for local control operation (para 2-12).
2-15. FREQUENCY HOPPING OPERATIONS
The programming for FH operation is stored in the ECCM module ROM. The control module executes these
commands to control the rt while in FH.
Received FH signals are digital. Received digital signals are bit synchronized by the switching module. The syn-
chronized FH signal is called BS DATA. See figure 2-4. BS DATA has been synchronized with internal rt clocks
and converted to rt signal levels. BS DATA is applied to the ECCM module deinterleaver. The deinterleaver
removes synchronization and frequency hopping information that is embedded in the signal. After deinterleaving
the signal is reclocked at a 16 kb/s rate. It is now called FH DATA, In X-mode, FH DATA is routed to the switching
module. In audio mode, FH DATA is converted back to an analog signal by the continuously variable slope
detector (CVSD) on the ECCM module. The RCV FH AUDIO output is routed to the switching module.
The ECCM module can process BS DATA or PT AUDIO during FH transmit.
ES DATA goes directly to the inter-
Ieaver. It is interleaved with the synchronization and FH information needed by the receiving rt to coordinate
communications. The CVSD converts XMT PT AUDIO to a 16 kb/s digital signal which is output as CVSD DATA to
the interleave. It too is interleaved with data, re-clocked, and output on the FH DATA line to the switching
The interleave supplies the control and data signals needed by the time sync/correlator. The correlators func-
tion is to synchronize the operation of the rt and the ECCM module. It manipulates control signal outputs such as
HOP-TIME and SYNC. These and others control rt operations in FH mode. They shut down reception/transmis-
sion during frequency shifts, provide the next frequency to the control module (via the data and address bus-
ses), and supply clocking for the ECCM module.
The ECCM module is also responsible for: storage of the FH operation programming, generation of random
numbers for hopping frequency selection, and processing and storage of FILL data. The rt chooses the frequen-
cies in FH by pseudo random number generation. The TRANSEC variable, sync time, and hopset net ID number
are used to select the next frequency. The control module uses the hopset and lockout set to create a look-up
table in memory of frequencies for the net. The ECCM module picks one of these frequencies from the table. The
result is passed to the control module over the data bus. The control module informs the rest of the modules of
the frequency selected by the SERIAL DATA LINE.