ASR-33 Data Format?

From: Hans Franke <>
Date: Wed Mar 31 16:16:29 1999

> I'm in the process of adding a
> teletype simulator to the COSMAC Elf simulator.
  ------------------ --------------------

> I'm simulating 110 baud with my "teletype", so most of the time
> the emulated 1802 and the emulated teletype sit there waiting for each
> other to send data.

> I'm using 110
> bits per second, no parity, 8 data bits, one low (logic 0) start bit,
> and one high (logic 1) stop bit.

My guess would be a timing problem, since both are simulations.
Do you run them on different computers with a real link inbetween,
or just within one machine using different tasks switched by the OS,
or do you have your own task switcher, or do the simulations run
in the same task ? How is the communication done ?

The idea with two stop bits as offered throughout the group is only
convieniant when using real hardware, since the stop bits give some
time for futher processing to the reciver.

For serial communication, a fixed time raster is esential, since
timing to detect a data bit is derivated from the start bit. The
whole gag of asynchronous communication is to detect the start of
a character to be transmitted and to keep within the timeframe for
the duration of this specific caracter. So if your simulations
runs in an cumbsy tasking environment (aka Win9x), you might get
undesired results, depending on the system services you use for
timing and communication.

Your result of getting always the same unpredicted result from the
same action might be based on this problem.


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Received on Wed Mar 31 1999 - 16:16:29 BST

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