On 9/6/2018 1:20 PM, Mia Magnusson wrote: > Not deriving the baud rate clock from the system clock must have added > to the cost. At that point, the crystal was a cheap item > > Of course you'd need a divisor that isn't as nice as 16 to get correct > baud rates with a clock that can also be used to generate a NTSC or PAL > color signal. If the 6551 addition had been in the plans when TED and > CPU were designed for the Plus/4 series, they might have had that > buildt in. If they really wanted to, they could have made it work: http://www.robotroom.com/Asynchronous-Serial-Communication-2.html But, the divisors in the IC were no doubt hardcoded and would have to be re-masked to be changed, meaning a spin of the IC. > > Btw a "6552" which can take color clock might had been something they > could sell anyways. There is a 65C52, with dual ACIAs. Jim > -- Jim Brain brain@jbrain.com www.jbrain.comReceived on 2018-09-06 21:00:37
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