Passport™ Trunked Systems - Motorola Professional Radio Service Manual

for customization for special requirements, and provision made to further standardized features to be
added to the protocol in the future. The standard defines only the over-air signalling and imposes only
minimum constraints on system design.
2.20.4 PassPort
PassPort is an enhanced trunking protocol developed by Trident Microsystems that supports wide
area dispatch networking. A network is formed by linking several trunked sites together to form a
single system. This offers users an extended communication coverage area. Additionally, users with
PassPort can seamlessly roam among all sites within the network. Seamless roaming means that the
radio user does not have to manually change the position on the radio when roaming from site-to-site.
For models which feature PassPort Trunking operation, the standard keypad board is replaced with
the PassPort Trunking Controller Board (PTCB). This board also provides advanced voice storage
features. Refer to Figure 2-2 for connector and signal routing from, to and through the Radio, PTCB
and Liquid Crystal Display (LCD) sub-systems.
2.20.4.1 Power Supplies
The radio supplies regulated Vdd of 3.3 VDC. This is used to power the Low Speed Data Filter and
Voice Storage circuits. The radio also supplies Switched Battery Voltage (SWB+). U612 regulates the
SWB+ to 3.3V which is applied to the PTCB microcontroller U601. A filtered voltage (Vdda) of _ Vdd
is developed by U603-4 and is used to supply a clean reference bias for the Low Speed Data filter
and Voice Storage circuits. The circuit of Q607 which can limit the voltage applied to the Voice
Storage chip is not used in portable applications and is disabled by 0 Ohm resistor R614.
2.20.4.2 Microcontroller (MCU)
PassPort Trunking operation is managed by the reprogrammable FLASH ROM based microcontroller
(U601). The MCU clock oscillator uses 8MHz crystal Y601 as a stable resonator. The PTCB
communicates with the main radio microcontroller by attaching to the same Serial Peripheral (SPI)
bus that passes though the PTCB to the LCD on the CLK, DATA, RDY, and MISO lines. The OPT_EN
line is strobed low only for communications with U601.
The MCU includes an on-chip Analog to Digital Converter (ADC). The received and filtered sub-
audible low speed trunking data waveform is applied to one of the ADC inputs. The software in the
MCU decodes and acts upon the trunking data.
The MCU includes a Digital to Analog Converter (DAC). As required, the MCU software generates
appropriate PassPort Low Speed Trunking Data waveforms. These are applied to the Low Speed
Data Filter and then to the radio transmitter modulation point. The amplitude of this waveform and the
resulting transmitted deviation is controlled by software.
2.20.4.3 Low Speed Data Filter
This analog circuitry is a 4 pole, 150 Hz cutoff low pass filter comprised of U603-1, U603-2 and
associated passive components. In receive mode, it removes noise and voice band signals leaving
only the low speed data waveform which is applied to the ADC input of the MCU. U608-4 isolates the
receive signal from the filter in transmit mode. When the radio is transmitting PassPort data, the MCU
DAC low speed data waveform is applied to the input of the filter which removes harmonics that would
interfere with voice and applies the resulting sub-audible data to the radio transmitter modulation
point.
2.20.4.4 Keyboard Circuit
The keyboard consists of a matrix of key switches and resistors as described in section 2.3. U605-2
monitors the column voltage and applies an interrupt signal to the radio microcontroller when any key
is pressed.
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Trunked Systems
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