Technical Manual

2-8 GUARDIAN VHF 110W MOBILE
2.4.6 FPGA
The control logic uses an Altera 8282 FPGA device to provide a flexible serial data routing function, I/O expansion
for H8 and DSP, clock generation, data multiplexing, and to absorb discrete logic functions.
The synchronous serial bus routing function involves routing the synchronous serial port of H8 either to the keypad
and LCD, or to the I/O expansion in the FPGA. High-order address pins from H8 control this routing and a FPGA
dummy write with dedicated FPGA chip select from H8. The FPGA includes a serial load parallel output shift
register that is used for parallel output expansion for H8.
The discrete logic functions of the FPGA, includes logic to control an inverter for one of the LCD control outputs.
The data multiplexing function involves rerouting serial pins between the accessory connector and the DSP SCI port
to allow data transmission and keyfill operations.
2.4.6.1 FPGA Configuration
The FPGA is configured at start-up from the main Flash memory using a serial load from H8. During configuration
outputs are tri-stated and pulled to a safe level by committing resistors to prevent audio and RF bursts at power up.
2.4.7 IF ADC
The IF sampling ADC is a 12-bit ADC capable of sub-sampling a 455 kHz, IF signal at 96 kHz sampling rate. It is
connected by a serial interface to the DSP ESSI port 1. The serial data interface is clocked at 1536 kHz.
2.4.8 Clock Generation
The clock generation logic is used to generate clocks for the synchronous power supplies, the ADC serial interface,
and the keypad microcontroller. The clock generator logic is implemented in the FPGA.
2.4.9 Logic Audio CODEC
The audio CODEC is an integrated ADC/DAC and audio filter device capable of full-duplex operation on voice
bandwidth signals at 8 ksps. The samples have a resolution of 13-bits linear. The CODEC is connected to the DSP
ESSI port “0” with serial data transfer rate of 2.048 MHz. The CODEC is continuously powered from the 3V logic
and 3V audio supplies. DSP parallel control lines are used to mute the input and output sections as required.
2.4.10 Accessory Connector Interface and Filtering
All outputs are filtered to limit their bandwidth to the minimum and current limited to protect them from output
short circuits to ground or up to 16V. All inputs are filtered and protected from continuous application of ground or
+16V. There is no protection against negative applied voltages. Inputs and outputs are protected from static
discharge of at least 10 kV air discharge. All inputs and outputs incorporate RF bypass filter capacitors adjacent to
the connector, except for ground.
2.4.11 Transceiver Interface and Filtering
Most of the signals crossing the interface are filtered to limit their bandwidth to the minimum consistent with correct
operation. Outputs from the control are filtered with series resistors on the RECM and grounded capacitors on the
transceiver adjacent to the connector. Outputs from the transceiver to the control use the reverse configuration.
2.4.12 Keypad Interface
Some filtering is provided on this interface, but all outputs are protected from short circuits by series resistors.
Where possible, inputs are also protected from damage by series resistors.
2.4.13 Audio Interface
The audio interface is implemented with four-way wire connectors directly via the 80-pin interface through the
Motherboard to the integral speaker and microphone.