User's Manual

15
MICROCONTROLLER
The DTX-142 handheld transceiver 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 Input is pulled LOW when the PTT input is grounded to initiate transmitter operation.
2 Input is pulled high when high/low power input is grounded. This produces a low RF output power.
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 TONE OUT generates the QC (CTCSS) or DQC (DCS) waveforms via an 8 bit PWM prior to
modulating the VCO in transmit mode. Also generates alert tones heard on the speaker.
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 supplies +5VDC.
19 Input is used to measure receiver RSSI.
20 AREF supplies the reference level for the A/D and is connected to the regulated +5 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 DTX-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.