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Top-level
 first attempt at PAL equations in galette--umm--did not match the real thing at all. i'm swapping parts into the DuPAL to compare how they perform for the same inputs. UNFORTUNATELY i've discovered that DuPAL cannot differentiate between a tri-stated output and a low output, even though the hardware is capable of doing that. 😩 44 comments
 bam! that was amazingly fast. so it turns out the output pin here, O13, used to drive the READY pin, goes hi-z when the drive select line is high. this is as expected. interestingly, it's driven either high or low when the drive select is low and the PAL is clocking out the drive ID code (1010... meaning it is a high density drive). I think it's time to probe this device in circuit. I've attached the Saleae to most of the pins of the PAL. you can see the drive ID protocol here. first it pulses the motor enable (with a drive select) to reset the state machine. then you get a bunch of pulses to clock out the data on the ready output (D7) and this is what happens when you put a double density disk in the drive. so the drive ID gets read every time there is a disk change, and the adapter changes the drive type depending on the disk! ok wow a few minor tweaks to the galette PLD file and the crazy thing works! I still need to test it with the Teac drive but I've managed to replicate the PAL. the PAL code is not very complicated. i was able to remove a bunch of terms that `espresso` added (spuriously). i also made some minor improvements. now for the most difficult part: what should i call my clone of "The Real HD-Drive"?  @tubetime  the layout for the board is simple. i'm making minor changes so it fits better in the Sony drive.
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@tubetime bit dramatic with the heavy traces; why not just use a couple of fills for power/gnd? @tubetime Okay, now melt them https://github.com/mitxela/kicad-round-tracks  @tubetime As "fartkontrol" is Danish, not German it's "den fartkontrol".  ok maybe this is better and somewhat more german. i kinda ran out of space for the text, which i guess makes it more authentic OK, i haven't fabbed it out yet, but I don't foresee any issues, so here's the repository! @tubetime amazing! If possible, could you add shots of the type plates of these drives? There are so many variants of the ones you mentioned. Hopefully us other drive modders can figure out how to modify the rest. 🙂 boards arrived! I can't wait to try it out but I need to buy some 34-pin shrouded headers. @tubetime Awesome work mate! Thanks for all your efforts! Can you please tell me on the Sony mod, is the JC40 a part that is desoldered from another location on the drive, or is it an additional one? (can't find it in the BOM) @tubetime Thanks a whole lot! BTW, are you having the pcb for sale anywhere, or upped on, say, pcbway? @salaxi nope, but it's easy to upload the fab package to your favorite service. @tubetime That's great! Just ordered a Sony to try this. Had a Power Computing external HD drive bought new decades ago, but its' GAL went kaputt. Time to get back in action..  @tubetime maybe you want to change driveselect to : gangwahl or fahrtwahlschalter :) @tubetime That's totally readable and, apart from the all-uppercase, looks pretty nice. It's been a long time since I've seen /, *, and + used rather than !, &, and | but it's charming.  @tubetime @RealGene yep, trouble is that i can't differentiate it from a regular logic high. one trick is to pull it to some other voltage and use a window comparator to detect it. |
Gregory's Server
oh i should just tag the guy who wrote DuPAL. @hkz very useful tool, can i have this tiny feature added to DuPAL Peeper? basically when you do a read, toggle the SIPO_O_7-14 lines and see if PISO_I_1-8 change at all. if they do, then they are hi-z.