Detailed Circuit Description; Mother Board Circuit Description; System Computer (Cpu) Board Circuit Description - Aeroflex NAV 2000R Operation Manual

2) Re-initialize the unit on-time and power on counter:
From within the Utility Menu option 5 selection, DISPLAY SYSTEM STATUS, the amount of time and
number of times the unit is powered on is displayed. With a new battery RAM module, these values need
re-initialization. This is accomplished by pressing, and holding down the 120 degree bearing "hot key" for
approximately two seconds.
3) Re-configure the NAV 2000R to the user's preference:
The user can now set the NAV 2000R to their desired configuration. This could be to set the GPIB
address, and External Modulation settings.
4) Re-calibrate the unit to insure good calibration constants:
Since the unit's calibration constants are contained within the battery RAM module, the unit must be re-
calibrated to insure the unit is producing the desired signals.
4.5 DETAILED CIRCUIT DESCRIPTIONS
The following sections cover provide detailed circuit descriptions and reference the schematics of Section
V.

4.5.1 MOTHER BOARD CIRCUIT DESCRIPTION

The mother board, located at the front of the card cage assembly, contains printed circuits that connect
the plug in assemblies; the CPU board, the DSP board, the Modulator module, and two optional cards.
All signals going between these assemblies, and to and from the front panel keyboard, are routed through
the mother board.
Power supply voltages are connected to the mother board at terminal block TB1. These voltages are
+15Vdc, +5.2Vdc, and -12Vdc. The 5.2Vdc voltage at TB1 -2 and -3 is split between two filters formed by
inductors L1 and L2 and capacitors C1, C2, C3, C4, and C5. These filter networks help isolate a +5v
digital power bus from a +5V analog power bus. The -12Vdc voltage at TB1-1 is routed to the Modulator
assembly mating connector J105, to Expansion connector J106, and to two voltage regulators U1, and
U2. Regulator U1 drops the -12volts to produce the -5 volt power bus. Regulator U2 drops the - 12 volts
to produce the -5 volt digital power bus.

4.5.2 SYSTEM COMPUTER (CPU) BOARD CIRCUIT DESCRIPTION

The System Computer Board is centered around the versatile 80C188 microprocessor and controls the
operation of the NAV 2000R. Reference JPN Drawing 02-5742-00 located in Section V of this manual.
The following sections discuss the System Processor Circuits.
The processor, U1, controls the keyboard, display, DSP processor board, RF Modulator Module, and
GPIB communications, and system timing. The processor uses memory mapping to address various
hardware devices. A feature of the system computer board is its use of battery backed RAM and
EEROM (Electrically Erasable Read Only Memory). The battery backed RAM enables NAV 2000R to
remember its last state through power ON/OFF cycles and provides a simple to use storage area for
calibration constants and instrument test set-ups.
NAV 2000R SIGNAL GENERATOR - REV. 0 – JULY 26, 2007 - PG 4-14
Aeroflex Operation Manual