Sailor RT2047 Technical Manual page 55

2 CIRCUIT DESCRIPTION RT2047 DSC - PART II
2.6.14 COMMUNICATION BETWEEN THE TWO MICROCOMPUTERS
The transmission of information between the 2 µC's takes place on a serial bus similar to a RS232C serial
interface. Each byte consists of 8 bits of information, a start-, a stop-, and a parity bit. Odd parity is being
used and the transmission speed is 2400 Baud but only one byte will be transferred in each period of 10
mS. Transmission can only take place when the DTR (PD1) is high. The µC on the KEYBOARD UNIT
will take this line high once every 10 mS.
Transmission from U19-6 to U9-7 Transmission is allowed on the ROD line (PC4) as soon as DTR is high
independent of the level of RTS. U9-7 will keep DTR high as long as it is receiving a byte.
Transmission from U9-7 to U19-6 U9-7 will set RTS (PD6 on U19-6) to a high level at the same time
as it sets DTR high. If U19-6 has nothing to transmit it will answer by setting CUTS (PC6) to a high level
as soon as it is ready to receive. After U9-7 has received the ready signal it will start transmission on the
TXD line (PD0 on U19-6). The DTR, RTS and CTS will be kept high as long as the transmission takes
place.
2.6.15 THE KEY-FUNCTION
When the transmitter is keyed the input PD2 on the Interface µC is put to a high level by the Keyboard
µC assuming that TX is allowed, TX can be prohibited when the RT2047 is operated as a slave over the
SP VHF Bus ( Described in section 2.7.5 The SP VHF Bus ). If the radio is tuned on a simplex channel!
the AF is muted by setting the output PB4 to a high level. Then the synthesizer is moved 4.6 MHz upwards.
Then the TX-VCO is turned on by setting PB3 high and after approx. 15 mS also the TX-BUFFER on (PB1
high) and after further 60 mS the PA-REGULATOR is turned on by setting PB0 and PB5 high. If reduced
power is selected PB5 will be low. When the key is released the PA-REGULATOR is turned off first. After
approx. 15 mS the TX-BUFFER is turned off, and after further 45 mS the TX-VCO is turned off. If the set
is in a simplex channel the synthesizer is moved 4.6 MHz back again, and the AF is turned on.
2.6.16 THE MICROCOMPUTER
The µC is held in reset by a low voltage on the RESET input pin. As long as the µC is in reset it is inactive
and all ports are configured as input pins. The 10V-SENSOR secures that the capacitor C54-6 cannot
be charged before the 10V supply is higher than approx. 8V. The 5V is checked internally. When the
voltage on the reset pin is above the internal comparator level the µC starts. First all pins on PA, PB, and
PC are configured as outputs. PB4, PB6, PC2, PC4 and PC5 to high level and the rest to low level. Then
the µC reads the address range from 64 to 0F in the EEPROM U8-6. If there is an error in the range from
64 to 77 the µC will transmit an "E0" message to the display and go to test mode. If there is an error in
the address range from 78 to 0F it will always initiate with channel 16, volume level at Pos. 5 and the
squelch level at 4. If the first test is passed the µC will send information to the VOL/SQ latch (U4-6) and
the RX-synthesizer and also initiate the selcall. Then the µC supervises the KEY-input (PD2), the squelsh
detector (PD7), the selcall detector (INT pin), the RTS-input (PD6), and the battery sensor. (See the
appropriate sections).
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