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Old 01-03-2009, 12:36 AM
Geoff Harrison Geoff Harrison is offline
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Join Date: Feb 2007
Posts: 104

Originally Posted by Pops Racer View Post
Now trying to figure out how to connect 2SIO to PC. I suspect both circuits are DTE and so must be 'crossed-over' (null-modem) TX -> RX, etc. Do you use DTR and RTS?
If you wire the port as per the MITS manual you end up with an odd hybrid DTE/DCE port. Tx and Rx are set up as though it is a DCE, but it uses the control lines as though it is a DTE. The 6850 requires CTS and DCD to be asserted, so you either have to tie them high in your cable, or give up on hardware handshaking and tie pins 23 & 24 to ground on the 6850 (remember, the signals are inverted on the board), in which case a straight cable will work fine using just the data lines and ground.

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