RF Technology Eclipse Series Operation And Maintenance Manual page 16

5 CIRCUIT DESCRIPTION
SPARE_SEL is a serial bus select. It has been reserved for future use, and has been
brought out to the rear DB25 connector. (see 5.1)
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)
Any GPS pulses are isolated from the on-board electronics by the opto-isolator U212.
The output of that opto-isolator is then connected to the GPS timer input of the CPU.
The software assumes that any GPS pulses are 1 second apart and can use this input to
measure the frequency error of the channel PLL reference oscillator. . It can then adjust
the channel reference oscillator to reduce this error to less than 0.3ppm. (See 5.1)
TERM_EN2 and TERM_EN1 are used to enable (when low) 600 ohm termination of
Line2, and Line1 respectively. (See 5.3)
Fo_MOD_2, and Fo_CHAN_2 are the Fo outputs from the Modulation PLL and the
Channel PLL divided by two. They should be 200Hz square waves, except for brief
periods when frequencies are being changed. (See 5.6)
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.
TX_LED, ALARM_LED, are CPU outputs that drive (when low) the TX LED, and the
ALARM LED on.
T/R_RELAY_H, when high, drives the T/R RELAY output low, and also enables the
RF power amplifier. The T/R RELAY output can activate at least one conventional
12V relay. (See 5.1)
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.
PA_CS is a serial select pin. It is passed, via the rear DB25 connector to the External
Power Amplifier (PA). (See 5.1)
DBGTX_TTL, DBGRX_TTL are RS232 transmit and receive (TTL) data pins which
are connected to the debug port after conversion to/from RS232 compatible voltage
levels by U202 and U201.
TXD_TTL, RXD_TTL, RTS_TTL, CTS_TTL, DTR_TTL, DSR_TTL, are RS232 data
pins which are connected to the main front panel serial port after conversion to/from
RS232 compatible voltage levels by U202 and U201.
PTT_uPHONE is a CPU input and it reflects the state of the PTT pin on the microphone
handset.
TONE_INT is a CPU input that comes from the FX805 (U500). This pin is used to
indicate when a Tone has been decoded, or there is some other need to service the
FX805. As yet this pin is not used in the T50. (See 5.5)
Page 16 RF Technology T50