16 TA2922 Universal Line Interface Service Manual
© Tait Electronics Limited March 2010
The default configuration is for ‘clean’ relay contact outputs in the form of two
isolated lines. A variety of relay contact options are available with the specific
population of option links, including 12V or DC ground permanently on one of
the contacts. The relay contacts outputs can also be configured for DC keying
output to the line for centre tap ‘phantom’ DC keying configuration.
An open collector output available as GATE_OUT_DIRECT can sink a 50mA
load. The voltage on this line must never exceed 45V.
2.4 Digital I/O
Five I/O lines from the radio internal options port, IOP_GPIO3 to IOP_GPIO7
are available as bidirectional inputs or outputs which can be connected to any of
the external D-range connector pins with the appropriate population of the I/O
matrix.
An exception is the use of the GPIO4 line. When this is activated (connected to
ground) on the radio IOP_GPIO4 as an output from the radio, the TA2922 enters
a disabled state where all transmit and receive audio and keying functions are
inhibited.
2.5 Serial Data
In the standard configuration, the microcontroller TX and RX data lines are
available as RS-232 inputs and outputs at internal connector S1 for serial
programming of the TA2922 board configuration and for board software upgrades
if required. The same RS-232 data lines can be routed to pins on the D-range
connector for programming the board without opening the radio lid. These lines
connect directly to a PC serial port for communication with the option board
programming software. See “Programming the TA2922 board with the PGM-
UIS” on page 41.
RTS and CTS hardware flow control lines are also available at RS-232 levels,
however, at the time of release, hardware flow control functionality is not a
supported feature of the option board software.
3.3V TTL logic levels are available as opposed to RS-232 levels. This involves the
removal of U8 and the fitting of components D13, R52, R53, R54, R55, R84
and R85.
The TA2922 may be configured to transparently pass serial data to and from the
radio internal option serial port through to the outside world. In this configuration
the same external TX and RX data lines are used for programming, but a power
up timer allows a short period of time where the programming application may
read or write to the TA2922 shortly after power on.
2.6 Microcontroller
A Microchip PIC 18F45K20 microcontroller, U1, forms the centre of the digital
processing, control and monitoring. The device is responsible for:
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