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Where are the missing signals that I can't pair between amiga external drive connector and gotek drive?

I'd like to connect GOTEK to CDTV, there is a way to do it directly (caddy died), but I can't find schematics for cable. I found this, both CDTV (left) and Floppy (right), but not sure where are all the signals and how to wire it up.

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I'd like to connect GOTEK to CDTV [...] but not sure where are all the signals and how to wire it up.

Simply connect either side according to names - they are the same on both sides, aren't they?

Signal  CDTV  Gotek
/CHNG    11     2
/MTRX     8     4 /MTRON
/INDEX   22     8
/RESET   10    --
/SEL0    21    10 
/SEL1     9    12
/SEL2    20    --
               16 /MTRON
/DIR     19    18
/STEP    18    20
/WD      17    22
/WE      16    24
/TRK0    15    26
/WPROT   14    28
/RD       2    30
SIDE     13    32
/RDY      1    34

but I can't find schematics for cable.

Maybe because it's straight forward? Commodore didn't invent the floppy, they simply worked with what was there, and noone likes to make complex cables. If you flip either connector upside down, you will notice that the sequence is the same on both sides, so a flat ribbon will do most of the work.

Where are the missing signals that I can't pair between amiga external drive connector and gotek drive?

Gotek is build after Standard (PC style) Floppies which use only 2 select signals (no need for SEL2) and don't feature a RESET.

MTRX/MTRON are the same signal, Motor-On. For PC style floppies there are two motor signals, but Amiga only supplies one - which doesn't really matter for the Gotek, so both can (should) be bridged.

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  • The diagrams show a SIDE signal (with no line over it) on the CN4 and _SIDE on the CN11. Is that a typo, or doesn't it matter (not used in this application), or do you need an inverter to make it work?
    – alephzero
    Aug 1 '20 at 12:39
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    Side holds a binary information (0=Side 0; 1=Side 1). Like an address line. It doesn't have an active state as both states are meaningful. Marking it as negative is rather useless - or have you ever seen an address line of a CPU marked as low active? Due some obscure reason (copy paste I guess) it is often shown as active low. But that doesn't matter. Adding an inverter will simply flip sides and make the drive rather incompatible. Would make a nice copy protection though.
    – Raffzahn
    Aug 1 '20 at 15:43
  • "Due some obscure reason (copy paste I guess) it is often shown as active low" Possibly the pin is pulled low if there is no connection - i.e. the drive is assumed to be single sided. (Just speculation...)
    – alephzero
    Aug 2 '20 at 22:00
  • @alephzero. A bar signals an active low signal. Not how it's handled or prepared. It makes only sense with signals that have an active state. SIDE doesn't have an active state, thus is should not have a bar. It's simply a documentation error. After all, not everyone drawing schematics (nowadays) is equally well trained.
    – Raffzahn
    Aug 2 '20 at 22:14

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