Codan NGT 2010 RF Technical & Service Manual page 659

NRI Microcontroller PCB
The NRI Microcontroller PCB is the main component of the NRI. It contains the main
microcontroller and associated memory, the CIB interfacing, and two peripheral devices
(a DUART and a CAN controller) required by the microcontroller to communicate
effectively with the system. It also supports the NRI Vocoder PCB.
Power supply and switching
Power to the NRI is from an external power supply, which is connected to either J101 or
J102. Relay K101 and associated circuitry provide reverse polarity and overvoltage
protection.
In Master Bus mode, IC102 supplies standby power, which is typically used for
illuminating the handset
current-limited power to the bus in Master Bus mode.
Different supply rails are required for different sections of the NRI internally. Most of
the analog circuitry (such as CIB system audio de-multiplexing/filtering) is powered by
the 10 V linear regulator IC111, which is of the low-dropout type so as to ensure that
regulation is maintained as supply voltage drops. Switching regulator IC112 is used to
generate an efficient high-current 5 V supply for the microcontroller and associated
components. The Vocoder module operates from the main 5 V rail and has on-board
regulators to generate any other rails required.
Codan interconnect bus
The NRI interfaces with components of the transceiver system using the CIB. For a
comprehensive explanation of how the CIB works see
description
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ICs 102 to 110 provide the audio sampling/filtering, while a programmable logic device
(IC101) generates the timing required to generate and reconstruct TDM signals. IC101
can either detect or generate synchronisation pulses as required by the master or slave
configuration. The CAN digital data interface is provided by IC208 (a CAN controller
IC) in conjunction with line driver IC204. The CAN protocol provides a high-speed
serial data transfer interface that is highly reliable and noise immune. The interface links
the NRI to other CIB devices, typically the NGT RF unit or junction box.
NGT Transceiver System Technical Service Manual
(2010)). The main components of the CIB include:
a main power source
a standby power source (always present)
a TDM audio interface (comprising up to seven simplex audio channels)
a 125 kbps serial data interface according to the CAN transfer protocol
key. A high-side switch, IC101, enables the NRI to supply
NRI—Technical description
page 69, NGT—Technical
265