On Thu, Aug 18, 2016 at 10:21 PM, Gary Hammond <[email protected]> wrote:
> Errr…no I wasn’t. > > I have not seen it mentioned in any of the documentation that I have read > so far and there’s no reference to it on the TPDD circuit diagram. The > pin-outs on the circuit diagram for the 8pin DIL connector on the back of > the drive do not show any VCC for a circuit housed in the DB25 shell, > unless it derives voltage via one of the handshaking lines. > > I have checked for continuity between the DIL8 end of the lead and the > DB25M end of the lead. Pins 1 (GND), 2 (CTS), 5 (DSR) and 7 (RXD) on the > DIL8 are directly connected to their equivalents on the DB25M. Pins 3 > (DTR), 4 (RTS) and 6 (TXD) on the DIL8 show resistance to their equivalents > on the DB25M so there is circuitry of some sort in there. I can’t tell if > it’s passive or active. > > Thanks for the tip! > Yes there are active electronics in the cables. It is believed to draw power from handshaking lines, probably DTR/DSR It does level conversion. No one knows for sure what's in there. If you're snooping a TPDD connection you definitely want to use a standard cable. -- John.
