[GreenKeys] Model 15 C-64 rate question

[Jeffrey D Angus]

On 7/5/2015 9:49 PM, drlegendre . wrote:
> But setting all that aside, I can't see how the TTY will cope with the
> character frames sent by the C-64. I see that you are setting 5 DATA
> bits and 2 STOP bits, but isn't the frame still 8 bits long (including 1
> START bit)? Isn't the TTY code 5 DATA bits plus 1 each STOP and START,
> for a total of 7 bits?
Actually, it's supposed to 1 start, 5 data and 1-1/2 stop bits.
> Seems like they'd fall out of sync after the first character. Last bit of
> the first character sent from the C-64 would become the first bit of
> the next character for the TTY, wouldn't it?
Being as how it's asynchronous, the TTY machine could care less about
how long the stop bit is (As long as it's at least 1-1/2 bits). When the
next start pulse comes in, it starts a whole new decode and print cycle.

At 45.45 baud, full speed (sending via tape for example) is 60 WPM.
At the same baud rate, if your stop bit is 44 mS (2 bits) instead of the
33 mS (1-1/2 bits) The actual printing speed on the receiving machine
will be 56.25 WPM.

The selector will sample somewhere around 11 mS into the stop bit
and trip the printer bail mechanism to make the machine "do some-
thing." It then gives itself another 22 mS or so to be "well and truly
stopped" (i.e., latching the main shaft clutch) while it waits for the
next start pulse.


-- 
Jeff-1.0
wa6fwi
http://www.foxsmercantile.com