CIRCUIT DESCRIPTION
AUDIO/LOGIC DESCRIPTION (ALL MODELS)
Address Bus
The address bus consisting of
A/D Converter Inputs
VRH/VRL - These inputs provide the reference voltages for the A/D converter circuitry. R115 and C105 attenuate noise present in the
PE0 - RSSI (Receive Signal Strength Indicator) input from limiter/detector U201 in the receiver. This signal is used along with the squelch signal to determine when valid data may be present and when to unmute the receive audio.
PE1 - Battery voltage input. The switched
PE2 - Power amplifier temperature input from thermistor R601 on the PA board. The DC voltage of this signal decreases as temperature increases.
PE3 - Lock detect input from synthesizer IC U804. If this signal is high (near 5 volts) the synthesizer is locked on frequency (see Section 3.7.6).
PE4 - Power switch sense input. This input is high when the power switch is on and low when it is off. When the off condition is sensed, the microcontroller saves the current settings and then powers down the transceiver by turning Q110 off (see Section 3.2.1).
PE5 - Ignition switch sense input. This input is low when the ignition switch is on and high when it is off. The microcontroller senses the ignition switch to control such features as the
PE6 - This input senses the voltage on the IN2 pin of data modem connector J301 and Option 2 slot
PE7 - This input senses the voltage on the IN3 pin of Option 1 slot
Serial Peripheral Interface Port (SPI), OR Gate (U103)
This serial port is formed by the MOSI, MISO, and SCK pins (31, 30, 32) of the microcontroller. It is a synchronous port which means that a clock signal is used to indicate when data on the data line is valid. This port has both master and slave configurations and in this application, the master configuration is always used. In the master configuration the microcontroller generates the clock and other signals.
MOSI (Master Out, Slave In) - This is the serial data output for the port.MISO (Master In, Slave Out) - This is the serial data input for this port.SCK - Serial clock output. This pin provides the clock signal to all devices served by this port.
This port provides
OR gates
Asynchronous Serial Communications Interface (SCI)
This is a full duplex serial port formed by the RxD (data input) and TxD (data output) pins (28, 29) of the microcontroller. This port uses a standard non-
| February 2001 |
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