On 10/15/2015 10:06 PM, Brent Hilpert wrote:
For working form modern equipment, the bit rates for all of them are potentially awkward. When working on the 28s, which were geared for 75 bps, I lucked out as I found the USB-serial interface I was using could do 75 bps - not entirely surprising as 75 is a factor of 2 down in the common 9600,1200,300 bps series. How many USB-serial interfaces are capable of this I have no idea. Regardless, the baud rates are slow enough that bit-banging from a program is not difficult, or an adjustable RC oscillator to a UART should do.
These were more common in the 8-bit area. Typically, a Z80 machine would involve a CTC and DART, so you could set the CTC count/divide for any reasonable rate needed.
This is probably the case also for many current MCUs that feature a built-in UART/USART or even designs using the Intel 8251--which often would be fed by an 8253/54. I believe the x86 "microcontrollers" such ash the 80186EB or NEC V20/V30 would also qualify.
For PC cards using UARTs with built-in divisors, simply changing the oscillator crystal would do the trick--IIRC, this was done with early MIDI setups.
--Chuck
