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high baudrate serial port use without serialDMA

Posted on 1998-06-26
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Last Modified: 2013-12-26
I am using a PowerBook5300C and need to read a few K data
from a device sending it over a serial line at 230k4 baud.

The PB5300 does not have the serialDMA driver, so using the
serial driver will only provide speeds up to 57k6 (the
extra csCodes for the 2 high baudrates do not work)

I know that LocalTalk operates at high speeds and does not
use the serial-driver.

Can anybody give me any reference/source/help/info on
how to implement this: reading a few K data at 230k4
without using the serial driver? (the cpu does not have
to do anything else during reading the data)

Thanks
Frank
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Question by:frb
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by:frb
ID: 1291464
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by:frb
ID: 1291465
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Accepted Solution

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agolan earned 150 total points
ID: 1291466
Localtalk uses SDLC framing to achieve the 230.4Bps.
SDLC = Synchronous Data Link Control.

Unlike what is known as "serial" or "rs232" communications,
that is actually asychronous communication, the SDLC is Synchronous, and it means that it need a synchronisation signal,
Apple induce this signal using something they called FM-0, also called "biphase space".
Note also that Appletalk needs RS-422 signalling, that unlike RS-232 is balanced, that is: there is a pair of wires for the data in each direction.
I know that they were "phonenet" attachment cables that used only a single pair of wires, but they converted the RS-422 data into some kind of modulation.

So the bottom line is that there is no good solution for you.

If you could tell a bit more about what you are trying to achieve, I might be able to help.

I had progarmmed telecommunications stuff for the Mac for several years (several years ago ;-) )
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Author Comment

by:frb
ID: 1291467
i found out that it is possible to use asynchronous communication
at 230k4. also somebody send me an example of how the SSC can be
accessed directly.
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