SYMEK FSK-9601, Руководство пользователя

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FSK 9601 Page 7
Jumpers for selecting the baudrate"
For setting the transmit or receive baudrate, you have to change not only the jumpers but some components of the analog
filters too. However, we explain the function of the related solder jumpers here:
TXBaud 9600 19200 38400 76800 153600 307200*
RX 2400 J2 + J6
RX 4800 J3 + J6 J2 + J8
RX 9600
J4 + J6
J3 + J8 J2 + J10
RX 19200 J5 + J6 J4 + J8 J3 + J10 J2 + J12
RX 38400 J9 + J6 J5 + J8 J4 + J10 J3 + J14 J2 + J14 J2+J12
RX 76800 J11 + J6 J11 + J8 J5 + J10
J4 + J12
J3 + J14 J2 + J14 J3+J14 J2+J14
RX 153k J13 + J6 J13 + J8 J13 + J10 J5 + J12 J4 + J14 J3 + J14 J4+J12 J3+J14
RX 307k J15 + J6 J15 + J8 J15 + J10 J15 + J12 J5 + J14
J4 + J14 J5+J12
J4+J14
RX 614k* J15 + J6 J15 + J8 J15 + J10 J15 + J10 J5+J14
RX 614k+ J13 + J6 J13 + J8 J13 + J10 J5 + J12 J3 + J14
J4+J12
RX 1228k+ J15 + J6 J15 + J8 J15 + J10 J5+J14 J15+J12
*: Xtal oscillator 19,6608 MHz instead of 9,8304 MHz
+: Xtal oscillator 39,3216 MHz instead of 9,8304 MHz
Test pins on modem FSK9601
You can access three test pins on the bottom side of the modem board:
MP1 (RX-Eye): AF-signal at the decider (comparator) input. Connect an oscilloscope to check the receiver eye diagram. s an.
MP2 (TX-Eye): Transmit signal at the D/A converter output. , unfiltered, transmit-eye diagram. Check the transmit-eye before
the antialiasing filter and modulation amplitude trimmer.
MP3 (PTT): MP3 is LOW (0 Volt) in receive mode, HIGH (+ 5Volt) in transmit mode.
Setting the Baudrate with FSK9601
The FSK9601 is available for various baudrates from 1000 Baud to 1,228 kBaud, baudrates of transmitter and receiver can be
configured to be different.
For setting the baudrate, it is necessary to:
ƒ
select the frequency of the master clock oscillator
ƒ
set the frequency dividers with the solder jumpers J2 to J15
ƒ
select the component values of the analog transmit and receive filters according to the baudrates.
Changeing the baudrate requires tools for smd part soldering and experience in handling such miniature parts. We do not
recommend to change the baudrate. We shall publish the instructions for changeing baudrate on http://symek.com later.
Known problems
A white noise spectrum contains components, which are recognised by the DCD circuit of the FSK9601 as valid data signal.
This cannot be avoided and may cause the DCD led to flash sometimes even if there is no data signal present.
If there is absolutely NO signal at the input (short circuit, no noise), it may happen that the last state of the DCD remains 'ON'
until there is a new signal at the input. The input signal should therefore be unsquelched, otherwise the transmitter could be
blocked due to an apparent busy channel. Countermeasures: A 1 MOhm resistor could be soldered parallel to R35.