Operations Manual

RF Technology R50 Page 13
5 CIRCUIT DESCRIPTION
5.2 Microprocessor (Sheet 2)
LINE_LEVEL_U/D and LINE_LEVEL_INC are CPU outputs which are reserved for
controlling a digital potentiometer in future.
COS_VOLTS_ON/OFF is a CPU output that when high applies 12VDC feed to COS+
terminal, so that the COS can be selected as +12VDC source or a free switch.
COS_POLARITY is CPU output that when low turns Opto-coupled transistor switch
U601on. It is controlled by the noise squelch detect, carrier squelch, or external
squelch signal
SQ is a CPU output that when low turns 600W line and direct audio path on. It is
controlled by the noise squelch detect, carrier squelch, or external squelch signal
N_BLK_EN is a CPU output that when low turns noise blanker option off.
CTCSS_SEL is a serial bus select pin. It is used to select the FX805 chip(U500),
which is used to decode CTCSS tones. (see 5.5)
PLL_SEL is a serial bus select pin. It is used to select the PLL chip in the PLL circuit
(U302). (See 5.6)
RCV_ADSEL is a serial bus select pin. It selects the quad Digital to Analogue
converter (DAC) that sets the levels for the 12MHz reference oscillator bias voltage,
21.855MHz oscillator bias voltage, noise squelch comparator bias voltage and the
LCD bias circuit. (see 5.4)
CH_EN is a serial bus select. It is brought out to the rear panel and is used to interface
to the channel encoder on the rear daughter-board. (See 5.1)
FLAT and DE_EMPHA are outputs logically inverted each other, when FLAT pin
low, the audio output is flat response, when DE_EMPHA pin low, audio is 750uSec
de-emphasized.
F0_PLL is the F0 outputs of the PLL chip divided by 100. They should be 312.5Hz
square waves, except for brief periods when frequencies are being changed. (See 5.6)
MON_SW is used to sense front panel MON.SQ switch.
LCD_DB7 is an input used to sense if the LCD display module is busy processing the
last command sent to it.
ECLK is a pin that at start-up only, should have the CPU system clock of 7.3728MHz
on it.
SQ_LED, ALARM_LED, are CPU outputs that drive (when low) the SQ LED, and
the ALARM LED on.
T/R_RELAY_H is a spare pin which is not used in R50 receiver.
SCLK, and MOSI are used as the core of a serial bus. SCLK is a clock pin, and MOSI
is a bi-directional data pin.