SWTPC 6800

On Thursday (08/04/2016 at 11:46PM -0700), Brad H wrote: On SS-50, the baudrate clocks are sourced from the CPU board onto approx 5 pins on the backplane. Originally, the top speed was 1200 baud and the MP-S and other cards would be jumpered to whichever clock (and therefore pin on the backplane) was the desired rate for that port. Over time, people wanted the ports to run at higher speeds and so would make a change on the CPU board (cut and jump, flip a switch, depending on design) to repurpose a backplane clock line from its original less desireable rate to a faster one. For example, 150 baud was seldom used and might get repurposed to a 9600 baud clock. So, you need to know something about the CPU board's design in order to know what clock rates get routed onto which backplane baud clock signals and then you need to know which backplane baud clock signal the MP-S card is connected to for its baud clock. These were almost always 16X clocks too, so if you scope the backplane signals, the rates you see should be 16 times what the baud rate is. Chris -- Chris Elmquist