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38400bps.lzh
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38400BPS.ENG
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Text File
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1994-01-22
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3KB
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78 lines
Translation by Arno Welzel
EMail: joey@zaphot.abg.sub.org
English is not my native language and i did only translate the most
important parts of the document.
If there are any problems in understanding this text, please contact me
(Arno Welzel) and not Jürgen Mayer. Thanks.
38400 bps for every ST/STE (c) 06.04.1991 by Jürgen Meyer
==========================
Jürgen Meyer
Karolinenstraβe 15
DW-2000 Hamburg 36
MausNetz: Juergen Meyer@HH2
E-Mail : Juergen Meyer@hh2.maus.de
This circuit is freeware. Private usage is allowed. Distribution via any
electronic media is allowed. Any commercial usage is _not_ allowed.
Altough this circuit is working properly in three different machines,
you can never exclude faults. Because of that i can not be responsible
for any damages caused by the usage of this circuit.
[Parts not translated]
This circuit consits of a TTL-chip, the 74LS74 (and a switch to choose
the high baudrate).
Every ST or STE can only use 19200 bps at the serial interface. This
limitation is caused by the clock-frequency of 2.4576 MHz wich is used
for the MFP-timers. The baudrate is set by the timer D of the MFP.
There where programs wich switched off the "divider" (sorry, i do not
know the correct word for german "Vorteiler") for the RC/TC-input of
the MFP.
The problem of this modification is, that the syncronization does not
work any more - so that there will by errors after every 16th, 32th or
64th byte. Because of that is not recommended to switch of the "divider".
[Parts not translated]
The circuit does the following: It gets the main-clock of 2.4576 MHz and
divides it to produce 614.4 KHz. This may be done very simple, by using a
RS-flip-flop to divide the clock by 1:4.
The 74LS74 consists of two RS-flip-flops. The first one is used to
get 1.2288 MHz. The second one gets the 1.2288 and produces 614.4KHz,
wich is needed for the RC/TC-input to use 38400 bps for the serial
interface.
[Parts not translated]
Building in
-----------
- Prepare the 74LS74 as shown in the images. [...]
- Carefully disconnect pin 16 of the MFP 68901 from the motherboard.
- Connect "XTAL in" to pin 18 of the MFP 68901.
- Connect "XTAL out" to pin 7 or pin 10 of the MFP. [...]
[Parts not translated]
The translator (Arno Welzel):
If you still want to use lower baudrates, you have also to build in a
switch. Normaly pin 7 and 10 are connected to pin 16 of the MFP for
"normal" baudrates. I hope this helps you.
[Parts not translated]