User's Manual

Decoding of the address space used by the U8 microcontroller is provided by decoders U23, U24, U21, and
U18. All decoder outputs are used for on-board devices except for U24-10, named ~EXT_CS. This output
defines the address space that is used to decode the Facilities CCA devices. Buffers U43 and U44 establish
an 8-bit asynchronous bus for communications to/from the Facilities CCA. The inputs and outputs of
buffers U43 and U44 as well as ~EXT_CS route to connector P2.
The U8 microcontroller has a synchronous serial port controller (SPORT) that is used for communications
to the off-board battery charge / power supply controller or controllers (Spare Slot). The SPORT signals are
buffered by U42 before connection to P2.
1.3.2.7 Facilities CCA Theory
Refer to Figure 1-13. The Facilities CCA provides system I/O for the RMS CCA. Many of the inputs and
outputs of the Facilities CCA eventually connect to the Interface CCA after routing through the Low Power
Backplane CCA. System_1 and system_2 battery-backed power supplies (nominally 48VDC) enter
connector P2 where they are diode-OR’D together and regulated down into several lower voltages;
including +24V, ±15VDC, ±12VDC, +5VDC, and +3.3VDC.
U1 and U7 DC-DC converters regulate the +48V down to +24V and +5V respectively. The +24V supply is
routed out connector P2 for powering the Interface CCA. The +5V supply powers several on-board digital
and analog integrated circuits as well as powering DC-DC converter PS1 to create ±15VDC. Several linear
regulators then create the ±12VDC supplies from the ±15VDC for powering RS232 integrated circuits and
the analog signal processing system.
All power supplies, including the system_1 and system_2 supplies, can be monitored by the RMS CCA
through the analog-digital converter. The RMS CCA will light on-board PWR_OK indicator CR24 if all
supplies are within range. The ~TEST signal, which originates at the LCU CCA and enters on P2-B8, will
light all on-board indicators when active. The ~TEST signal will also cause audio to be emitted from
speaker SPK1 when active.
The ~MRESET signal, which originates at the LCU CCA and enters via P1-B16, resets U8 when active. U8
outputs ~RESET, which clears the outputs of all on-board latches. ~RESET is also asserted by U8 if the
+3.3V supply drops too low.
An asynchronous data and address bus provided by the RMS CCA enters via DIN41612 connector P2. The
address bus is decoded into 10 segments for input buffers and output latches. Input buffers are the U27 A-D
converter bus, U28 and U29 system configuration switches, U31 amplifier powers status, U32 monitor
powers status, U18 frequency configuration switches, and U37 TACAN antenna status. The output latches
are U22 A-D converter control, U23 Ident tone multiplexer control, and U38 TACAN antenna control.
As mentioned previously, all power supplies can be monitored by the RMS CCA through on-board U26 A-
D converter as well as the U30 voltage reference, exterior and interior temperatures, ten spare analog
inputs, and four spare digital inputs. Exterior and interior temperatures originate at the Interface CCA and
are conditioned by U19:A and U19:B operational amplifiers. The spare analog inputs and spare digital
inputs also originate at the Interface CCA. All of these analog signals are switched through U20 and U21
multiplexers to the single channel A-D converter and read digitally via buffer U27.
The system configuration switch signals, SCON0 through SCON15, originate on the Low Power Backplane
CCA and enter via DIN41612 connector P1. Two of these configuration switches, DIALUP/~EXT and
DED/~RADIO, determine whether U12 and U14 on-board modems or external modems connected to the
Interface CCA are active. If the U12 and U14 modems are selected, they communicate to the RMS CCA
serially once their TTL signals are converted to RS232 by U11 and U13. The U12 and U14 modems each
have a speaker output which is multiplexed through U16 to the U15 amplifier and SPK1 speaker. Both U12
and U14 modems have on-board tip and ring transient voltage suppression (TVS) before eventually routed
to the Interface CCA and more TVS protection.