Electronic Systems TRS-80 Serial I/O Board?
jnc at mercury.lcs.mit.edu
Wed Jun 14 09:44:47 CDT 2017
> From: Brent Hilpert
>> The trimpot on the board says to me that the clock is most likely a
>> simple RC affair.
> There's a 7493 (4-bit counter) on the board as well, which looks to
> have connections to the dip switches beside it, in all likelihood the
> baud rate divider and rate selection
Yes; but the trim pot is also there because one has to set the basic clock to
one of two values, depending on whether one wants the 150/.../2400
selections, or the 110/etc selections; one has to set it to 26 usec for the
former, and 35.5 usec for the latter.
So drift would have been an issue, but not initial component values...
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