Question about modems

Brent Hilpert bhilpert at
Thu Nov 14 23:59:20 CST 2019

On 2019-Nov-14, at 9:30 PM, Jim Brain via cctalk wrote:
> On 11/14/2019 11:05 PM, Brent Hilpert via cctalk wrote:
>> (Without having gone through the code presented in full detail, but thinking from root premises.)
>> ASCII A = 0x41 --> 2 bits on
>> ASCII T = 0x54 --> 3 bits on
> I agree, though I believe aT,At,AT,and at are all allowed, which complicates things a bit aT is the bad one, where the calc for 7E1 and 7S1/8N1 yield the same values...

... right, was forgetting about case.
But if you're trying to account for mixed case, I don't think the CR resolves it anyways:

ASCII  A = 0x41 --> 2 bits on
ASCII  T = 0x54 --> 3 bits on
ASCII  a = 0x61 --> 3 bits on
ASCII  t = 0x74 --> 4 bits on
ASCII CR = 0x0D --> 3 bits on

In sequence "Ta<CR>", all characters have an odd number of bits on and would produce the same parity value, and collectively would be indistinguishable from a corresponding constant M or S parity.

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