Maxon Telecom SP200, SP210 5 DETAILED FUNCTIONAL DESCRIPTION

SP200/210 Maxon SP200/210 Radio

Issue 1.0 DETAILED FUNCTIONAL DESCRIPTION

03/01 Page 5-1

5 DETAILED FUNCTIONAL DESCRIPTION

This section provides a detailed description of the opera tion of the radio.

Power Circuits

Battery voltage, or external voltage through the access ories connector, is applied via a 4A fuse (plus

diode protection) directly to the RF power module and, after th e on/off switch, to the dc to dc converter

and voltage regulator. The majority of the circuitr y is powered via IC1, which regulates the +7.5V dc

supply down to +5V.

Transistors Q2 and Q32, in conjunction with the Tx Enab le and Rx Enable lines from the

microcontroller, apply +5V Tx or +5V Rx to the releva nt circuitry during receive or transmit. Thus, f or

instance, the receive front end amplifier is only po wered during receive and the power control IC is

only powered during transmit.

It is possible to program the radio for power saving. This mode causes the microcontroller to pulse the

Rx Enable line high and low for periods between 100 and 300m S. The time may be selected when

programming the radio. As soon as the radio detects a si gnal it switches into normal mode.

Microcontroller

The microcontroller (IC403) is a One Time Programm ed Processor chip based on the Hitachi HD3837

processor with onboard ROM and RAM.

It controls all functions performed by the radio, in conjunc tion with control signals from push buttons,

switches etc. It controls the data to/from the EEPROM and to th e PLL IC, Audio ASIC as well as

controlling external data from the programmer and alignm ent interface. The microcontroller generates

the enable lines, controlling routing of signals and the in dicators (LED,LCD and bleeps).

The microcontroller also generates and decodes the SAT tones (filtered by the ASIC).

EEPROM

Relevant channel information, such as Rx / Tx frequenc ies and CTCSS / DCS codes, is stored in the

EEPROM (IC404) which is a X25330. This information m ay be programmed and erased via the

accessories socket. Certain parameters can also be altered via the pushbuttons and keys on the

radio, i.e. scan channels and priority channel. T he EEPROM has 32768 (8x4096) capacity and data is

written serially.

Channel Select Circuit

Up to 199 channels may be selected, using the channel k eys on the front panel. Pressing the channel

keys earths pins 40 and 41 of the microcontroller, so enabli ng the decoding for the appropriate Rx and

Tx frequencies, and associated data, to be selected from the EEPROM.