Jeff wrote:Another point : can you take some oscilloscope pictures of the Write Data line synced on the Write gate line during sector writing ?
I borrowed a DSO. See the attached photos. The second photo shows that "data" begins to appear on WD about 180us after WG goes low.
So if understand well you have added a pull up and a pull down resistor ?
Yes, see the drawing. A typical termination is 220 ohms to +5 (but I used 270 because of the 1K already on the emulator) and 330 ohms to ground. That equates to a termination impedance of about 129 ohms which is ideally near the impedance of the cable to minimize reflections but more importantly it is low enough to charge the cable capacitance quickly. The line driver is open-collector and requires an external pullup. The resistor network effectively connects it to +3V through 129 ohms. 3V is well above the logic "1" threshold, at least for TTL.
Connect it on a PC and try to write something on a ms dos floppy disk image.
I connected it to an HP Vectra and after I learned to set the "File Interface Mode" in Settings to "IBM PC 1.44MB" before exporting to .hfe (I see that it sets a byte in the .hfe file), it worked. I was able to write to the emulator on the Vectra.
I have been using the default Shugart File Interface Mode for the SORD and my 50-to-34 pin adapter follows the Shugart pinout. Does the File Interface Mode choice have any effect other than changing the pinout?