10
DR-142 THEORY OF OPERATION
MICROCONTROLLER
The DR-142 receiver is electronically controlled by U301, an 8-bit flash programmable microcontroller.
U301 has A/D inputs and PWM outputs for processing analog signals. Radio characteristics are stored in
internal EE memory. Its RS232 port is used in programming the radio’s personal characteristics such as
frequencies and tones.
PIN
DESCRIPTION
1 N/A
2 N/A
3 GROUND
4
+5 VDC V
CC
supply voltage.
5 GROUND
6 +5 VDC V
CC
supply voltage
7 XTAL1 is 14.4 MHz reference input from Y301.
8 Input is normally high when PLL is locked and low when unlocked.
9 Output goes high to produce high power RF output.
10 Output drops low momentarily to produce synthesizer latch enable (LE) pulses.
11 Output goes high to enable receiver (RXEN).
12 Output goes high to enable transmitter (TXEN).
13
N/A
14
SQUELCH output goes high to apply power to audio amp U306 for receiver speaker audio or
radio alert tones.
15
DATA output sends serial data to frequency synthesizer U401 to program frequency information.
Also used for flash programming (MOSI)
16
CLK output sends serial data clock pulses to frequency synthesizer. Also used in flash
programming (MISO).
17
output is set permanently low to allow CS0 to be a channel select input bit.
18 AVCC su5VDC.
19 Input is used to measure receiver RSSI.
20
AREF supplies the reference level for the A/D and is connected to the reg5 VDC.
21 AGND supplies A/D ground.
22 Not used
23 Input is pulled low when the CS2 frequency bit input is tied to ground.
24 Input is pulled high when CS0 channel select bit is pulled low.
25 Output is set permanently low to allow CS1 to be a channel select input bit.
26 Input is pulled high when CS1 channel select bit is pulled low.
27 CTCSS IN is an A/D input sampling the CTCSS or DCS waveform.
28 Not used
29 RESET is held low to start the radio in a known state on power up.
30, 31 SERIAL DATA PORT links the microcontroller to communications from an external data terminal
via programming port pin 9 of J301. This allows programming of the DR-142 EE memory used
to store channel frequency and configuration information.
32
CARDET gets pulled low when a RF carrier is detected by the U101.
