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The microcontroller also monitors power amplifier ambient temperature and voltage and cuts back power or disables the transmitter if either are excessive. 3.2 POWER DISTRIBUTION AND SWITCHING 3.2.1 POWER SWITCHING CONTROL A diagram of the power distribution and switching circuits is shown in Figure 3-1. The main power switching is performed on the RF board by Q510 and other transistors. This switch is controlled by the front panel power switch, the ignition sense input, and the microcontroller as shown in Figure 3-2. For the front panel on-off switch to be detected, Q109 must be turned on by a high signal applied through R170 or from the ignition switch. R170 is installed if the ignition switch is not used to control power. Q107 and Q108 provide power switch on and ignition on signals to the microcontroller so that it can sense those conditions. Q110 allows the microcontroller to hold power on for a time after it has been turned off by the power or ignition switch. For example, when the microcontroller senses that power was switched off by the front panel switch, it holds power on for a short time so that switch settings can be saved to memory. It also holds power on when a power-off delay is used. Once power turns off, power is also removed from the microcontroller. Therefore, power can be turned on only by the power and ignition switches. NOTE: The front panel power switch is a push on, push off type (pressing it toggles between open and closed). It is not a momentary switch. 3.2.2 SUPPLY SWITCHING When power is turned on by the front panel power switch, the base of Q514 on the RF board is grounded through the power switch. Q514 then turns on which also turns on the Darlington amplifier formed by Q511 and Q512. These transistors are turned on by a 13.6-volt signal applied through R535. Series-pass transistor Q510 is then turned on and 13 volts appears on its collector. The diodes in CR505 and CR506 become forward biased only if the 8-volt supply applied to the collector of Q514 becomes shorted. This provides current limiting which prevents damage to the transistors. Q513 controls the Q511 base current in order to maintain approximately a 0.8-volt drop across the emitter and collector of Q510. This provides noise February 2001 3-2 Part No. 001-9800-001 CIRCUIT DESCRIPTION POWER DISTRIBUTION (ALL MODELS) + Chassis GroundVehicle Battery 15A Fuse Power Cable Power Amplifier Board Transceiver Power Connector CR600 Transient Suppressor Unsw Bat Unsw Bat Sw Bat Unsw Bat J600 J201 1 2 11 J501 J302 F500 4A Q510 Switch Front Panel On-Off Sw U501 U105 8V Regulator 5V Regulator 8V 5.5V Regulator 8V Tx Switch U502 Q504 5.5V 8V Tx From Shift Reg U801 From Latch U112 A/L Bd Sw Bat 2 5 15 Sw Bat 8V Vcc 12 J100 J3 Sw Bat Sw Bat Sw Bat J2 J1 2 5 J1 Microphone Jack Display Board Interface Board Audio/Logic Board RF Board R533 F100 2A R2 High Tier On-Off Sw On-Off Latch (A/L Bd) Low Tier 4 10 11 High Tier Only Figure 3-1 Power Distribution and Switching Audio/Logic Board RF Board Interface Board (High Tier Only) Power Switch Ignition On Sense Sense Supply Front Panel On-Off Sw 20 18 J3 J302J100 J201 Q107 Q108To uC, Pin 60 To uC, Pin 62 Q110 Unsw Bat Unsw Bat Q510 Switching Circuit Q109 Sw Bat U113A-D Power On-Off Latch Low Tier Only 51 R170 Power Hold From Ignition From Shift Reg Switch Note:Arrows Indicate Signal Flow. U111, Q7 This Resistor Installed If Ignition Sense Not Connected Figure 3-2 Power On-Off Control Circuit filtering of the 13.6-volt supply. The emitter of Q513 is biased at about 4.5 volts by R538 and R542 (with a battery voltage of 13.6 volts). CR504 mirrors the base- emitter voltage of Q513, and the voltage across R541 is the same as the voltage across R542 when the voltage applied to R536 is approximately 12.8 volts. Noise pulses less than 1.6 volt P-P then do not appear on the output of Q510 because of the emitter voltage filtering provided by C565. This reduces the amount of noise applied to circuits powered by the switched 13.6-volt supply such as audio power amplifier U306. Additional filtering of the switched and unswitched battery supplies is provided by C548C553. Resistor R534 turns Q514 off when power is turned off. February 2001 3-3 Part No. 001-9800-001 CIRCUIT DESCRIPTION AUDIO/LOGIC DESCRIPTION (ALL MODELS) 3.3 AUDIO/LOGIC BOARD DIGITAL CIRCUIT 3.3.1 MICROCONTROLLER (U101) General The control logic is based on an MC68HC11F1 eight-bit microcontroller (U101). This device has an internal 1K-byte static RAM and 512-byte EEPROM but no internal ROM or EEPROM. Therefore, all program memory is contained in the external flash memory device (U108). In addition, the microcontroller has several general purpose input and output pins, an eight-channel A/D converter, and synchronous (SPI) and asynchronous (SCI) serial ports. The A/D converter port allows analog signals to be monitored such as the power amplifier temperature, RSSI signal, and vehicle battery voltage. Separate buses are used for data and memory...

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