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! From: M100 [mailto:[email protected]] On Behalf Of eddie edwards Sent: Friday, 19 August 2016 1:17 PM To: Model 100 Discussion <[email protected]> Subject: Re: [M100] TPDD/TPDD2 boot disk captures (Take 2) "Looking at the schematic for the TPDD, it would appear that the TPDD is not true RS232" you are aware that there is circuitry in the TPDD cable? _____ From: M100 <[email protected] <mailto:[email protected]> > on behalf of Gary Hammond <[email protected] <mailto:[email protected]> > Sent: Thursday, August 18, 2016 9:30:40 AM To: 'Model 100 Discussion' Subject: Re: [M100] TPDD/TPDD2 boot disk captures (Take 2) Looking at the schematic for the TPDD, it would appear that the TPDD is not true RS232. It is only swinging between 0v and 5v with voltages outside of that range being shunted to gnd/vcc via diodes. The model 100 on the other hand appears to use vee/vcc voltage swings that are probably RS232 compliant or at least closer to what they should be. I could use a MAX232 chip and loop the RX and TX lines through it to regenerate the signals.might try that over the weekend. From: M100 [mailto:[email protected]] On Behalf Of Gary Hammond Sent: Wednesday, 17 August 2016 8:28 PM To: 'Model 100 Discussion' <[email protected] <mailto:[email protected]> > Subject: [M100] TPDD/TPDD2 boot disk captures (Take 2) . I have not yet succeeded in capturing the TPDD backup of the boot disk. There is just enough bleed to the serial sniffer to stop the backup process commencing after the destination disk has been formatted. The backup program hangs at the end of the format routine and there is no disk activity after the heads return to the start position. Normally there looks like a head seek to read a directory at the end of the format. If I take the serial sniffer out of the circuit, the backup process works fine. I have tried with 2 different TPDD's and I get the same result. Maybe the serial com circuit is more sensitive in the TPDD's. I may need to make up an external serial buffer to boost the RS-232 levels. .
