User's Manual

Eclipse2 Technical Manual V1.5 Page 12 of 16
(down to 0Hz DC) signals, the DC offset of input signal is shifted by the bias circuit which is
controlled by the RISC processor to give the maximum dynamic range for the ADC.
The CODEC has two identical channels, the output of channel 1 is used for line output. PCM signal
from the DSP is decoded to analog audio, and amplified, buffered by op-amplifier U10, coupling
through the line matching transformer (T2), and sent to the RJ45 E/M Line connector and the D25
system connector.
The channel 2 output of the CODEC is used for monitor speaker, PCM signal from the DSP is
decoded to analog audio, amplified by a Trans-conductance amplifier (U11), this amplifier is used
as the speaker volume control. The power amplifier (U13) provides additional power gain to drive
the internal and external speaker.
A 16-bit DAC (U14) converts the digital output from the DSP to analog signal, the signal is filtered
and buffered by op-amplifier (U10), then sent to the D25 system connector. The amplifier is DC
coupled, the DC offset can be set by the bias circuit which is controlled by the RISC processor. This
output is useful for low frequency application such as sub-tone, and NRZ digital signals.
I/O and Controls
The RISC processor uses serial buses and GPIO to control the base station.
A 10-bit 11-channel ADC (U7) senses the following signals and passes the data to the RISC
processor via serial bus:
Channel 0: exciter PLL tuning voltage
Channel 1: exciter forward power of the power amplifier
Channel 2: exciter reverse power of the power amplifier
Channel 3: receiver PLL tuning voltage
Channel 4: Interface board temperature
Channel 5: Input power supply voltage
Channel 6: receiver power supply voltage
Other channels are reserved for future use.
A 10-bit 8-channel DAC (U6) converts data from the RISC processor serial bus to analog voltage
for following functions:
Channel 0: monitor speaker volume control
Channel 1: 600 ohm audio Line input gain control
Channel 2: exciter reverse power of the power amplifier
Channel 3: AUX audio input bias setting
Channel 4: AUX audio output bias setting
Channel 5: receiver IF amplifier gain control (not used in release1 RX module)
Channel 6: exciter RF output power control
Channel 7: exciter VCO bias setting
Channel 8: receiver VCO bias setting
The op-amplifiers (U4, U28) are used for converting DAC output to proper voltage which is required
by the system hardware.
The Interface board accepts both TTL PTT input and E/M signaling, the TTL PTT is buffered by Q4
and Q5, E/M signal is isolated by Opto-coupler U3 to system I/O level. The output of the RISC I/O
logic is buffered by U1,Q1-Q3 for interfacing the external logic. The solid-state relay Opto-coupler
is used to isolate the system I/O from E/M signal.
A dual retriggerable monostable multivibrator (U5) in the circuit is functioned as a IRQ generator, it
senses the changes of the Input logic and sends a narrow pulse to the RISC processor for trigging
the processing IRQ.
U31 is a USB to RS232 bridge which transfers the USB data between the front panel connector and
the system serial bus. U9 is an transceiver which converts RS232 +/-15 logic from the rear panel
to serial bus level. U30 is a bus switch to select one of above passing through to the RSIC
processor.