DragonDOS Cartridge/Controller Schematics

To ensure correct operation of the disk drives, the WD2797 in the DragonDOS controller needs to be correctly calibrated. There are a number of different suggested values, for example Western Digital suggests 450ns for TG43 (TP3), NDUG** 600ns and data sheets from 2797 clones 500ns. I recommend you try the suggested settings below and if still experiencing difficulties try the NDUG values. To perform the calibration you will need an oscilloscope.

Instructions:

• Remove the top from the disk controller

• Plug into the Dragon as normal and turn the Dragon on

• Connect TP1 (TEST) to TP5 (GND)

• Scope TP4 (DIRC)

• Adjust C1 to 250Khz

• Scope TP3 (TG43)

• Adjust POT1 so that the pulse width is 500ns (600ns NDUG)

• Scope TP2 (WD)

• Adjust POT2 so that the pulse width is 250ns (300ns NDUG)

** National Dragon User Group