Testing my new seek logic for the Virtual 2315 Cartridge Facility - part 11

STILL FOCUSING ON SIGNAL INTEGRITY FOR V2315CF SEEK

I was not happen with the glitching and malformed signals going into the 1130 for the +Access Ready feedback signal. I am determined to clean this up and not just hope that the Virtual 2315 Cartridge System (V2315CF) works in spite of the signal distortion. The first thing I did was to remove the terminator resistors for that signal, to see what the signal looked like. It was still distorted.

The new version of the 2310 Interface Board, fabricated and current being shipped to me, adds electronic switches to short the signals between the disk and the 1130 while in real mode, rather than trying to generate the signal as a copy of the incoming one. I installed a short bit of twisted pair to bridge the B07 pin from the disk drive to the B07 pin heading into the 1130 disk controller circuitry. The result was considerably better.

The blue trace on the bottom is the +Access Ready signal generated by the disk drive and the yellow trace is the same signal at the entry to the disk controller SLT cards inside the 1130. The green trace is the -Access Go signal that goes from the 1130 to the disk to start a seek. Finally, the purple trace is the -10 Mil Step signal, which initially requested a single track move and then rose so that the additional steps are two tracks each. 

The temporary bridge connecting the signal straight through

Above is a trace of a seven cylinder seek. The -10 Mil Step signal is low for the first step and high for the next three. It does look good, although with a time scale of 5 milliseconds per division any glitches wouldn't be visible there. 

V2315CF AND 1130 IN PERFECT SYNC, DISK SOMETIMES IS OFF

I pounded away at the disk trying small, medium and long seeks in both directions. I was pleased that the disk arm position is now exactly in agreement. The only issue is that the V2315CF shadowing of the arm position sometimes drops a few cylinders from the count. 

I am hopeful that the new PCB with its electronic switches will further improve the fidelity, as it will manage seven signals that run between the disk and the 1130 controller circuitry. By the end of the week I should have built the new version of the board and installed it. I can troubleshoot further if the issue is still present with the new board version. 

VERIFIED THE POWER FAIL PROTECTION

I wired together the elements that give the V2315CF the ability to detect a power failure in the 1130 and conduct a full writeback of the RAM contents into the mini cartridge leveraging a 12V motorcycle battery. 

The power distribution unit board, in the center of the photo above, routes power between the 1130 12V rails, the motorcycle battery, a smart trickle charter, a timer module, the power supply for the V2315CF and then the V2315CF unit itself in the lower left. At the top is a bench power supply that stood in for the 1130, allowing me to flip it off to verify that the timer powers the unit during a 40 second interval, and that the V2315CF properly detected that the 1130 12V power dropped. It is ready to be wired into the 1130 system. 

WILL MAKE ADJUSTMENTS OF THE INTERNAL DISK DRIVE SETTINGS

The internal disk drive has a set of six adjustments that are important to proper behavior. These include the thresholds for the 10 and 20 mil seeks, the timers for the various actions during a seek, and the sensitivity of the seek movement circuitry. Those, coupled with the mechanical stops at cylinders 0 and 202, will ensure the most reliable operation.