Motorola APX 7500, Подробное руководство по обслуживанию

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68009482001 September 9, 2011
Theory of Operation: System Communications Overview 2-3
2.2.7 Headset Microphones 4.8 Volt Regulator
U1306 is a Texas Instruments TPS71501 low drop-out adjustable regulator with an output current of
50mA. The voltage is set to within 5% of 4.8V (4.8V_BIAS). This voltage provides the bias for both
headset microphones’ internal circuitry. This regulator is self enabled with SWB+ as the input
voltage.
2.2.8 Headset Volume Control (RX Audio Attenuator) Voltages
U1320 is a Texas Instruments TPS71501 low drop-out adjustable regulator with an output current of
50mA. The voltage is set to within 5% of 9.6V (9.6V_AA); furthermore, using a voltage divider circuit,
the 9.6V is divided down to 4.8V (4.8V_AA). 9.6V_AA is used to power the RX Audio Attenuator
U506 as well as the dual buffer op amp package U501 which follows the U506 output. 4.8V_AA
provides the reference for the audio input signal to U506. This regulator is self enabled with SWB+
as the input voltage.
2.3 System Communications Overview
The O5 control head communicates with the radio transceiver and the Mainboard via the CAN
(Controller Area Network) bus interface and is set up in remote mount configuration as noted in the
O5 manual. Likewise, the radio transceiver is also in remote mount configuration and uses cabling
internal to the Consolette to connect to the O5 control head and the Mainboard via CAN. The CAN
interface is described below.
The front panel keypad and display are connected to the Mainboard via ribbon flex cables. The GCAI
connector for programming and keyloading uses an internal cable to connect to the front of the radio
transceiver directly while the power indication LED has two wires connected to the Mainboard.
The radio transceiver also connects to the Mainboard via a ribbon cable that attaches to the 25-pin
front connector on the remote TIB interface.
Additionally, the Consolette has many communication ports on the rear panel. There are eight (8)
RJ-45 connectors, a USB device (type B) port, a USB host (type A) port, a 3.5mm audio jack, a
DB25 accessory connector, a 14-pin accessory connector, and one or more RF connectors. All of
these ports are attached to backplane boards which are connected to the Mainboard via two ribbon
flex cables, with the exception of the RF ports which are connected directly to the radio transceiver.
2.3.1 CAN Interface Communications
The Mainboard contains an FPGA that is used to convert SSI signals into a robust signaling protocol
that can travel over several meters of cable. A Controller Area Network (CAN) is used for this
purpose. The CAN bus is a differential bus operating at approximately 1MHz. The signals are sent to
the radio transceiver and the O5 control head where identical FPGA’s convert the CAN signals back
to SSI and route the SSI signals to the microprocessor in each device. This is a bidirectional bus
allowing each device to send messages to each other and also back to the Mainboard using the
same CAN bus. Two CAN buses are used as separate differential pairs to transfer data and audio
between all devices. These are labeled CAN1 and CAN2, where CAN1 carries audio and CAN2
carries data. A third CAN bus is used for system on/off/reset commands. All three CAN bus twisted
wire pairs are contained in each single cable.
The CAN1 bus is used for all audio exchange between the Mainboard, O5 control head and
transceiver. The O5 control head converts microphone signals received on the GCAI to SSI using a
CODEC. In addition, received audio from the transceiver is sent to the control head on this CAN bus.
The FPGA on the O5 control head converts the CAN data back to SSI and routes the signal to a
CODEC. The CODEC converts the audio back to an analog signal and routes the signal to an audio
PA in the control head. That audio stream is then sent to the speaker mounted in the front panel of
the Consolette.