Connector:2nd disc drive (CPC664, CPC6128, CPC6128+)

From CPCWiki - THE Amstrad CPC encyclopedia!
Jump to: navigation, search

Make sure to read the warning below!

2nd Disk Drive pinout


The following table lists the signal on the "2nd Disk Drive" connector on the back of the CPC664/CPC6128/6128plus.
Signal names in simple brackets show the meaning the signal has today. For your convenience, the pin no. are given as specified in the Shugart standard first, followed by the pin no. as assigned by Amstrad and shown in the manual.

Pin No. (Shugart) Pin No. (CPC) Pin No. (6128plus) Signal Name Description
n/a "35" n/a N/C Schneider CPC6128 only
1 (red wire¹) 34 none - spare wire^4 GND Ground
2 33 1 N/C (/REDWC) Density Select 1=Low/0=High
4 31 3 N/C Reserved
6 29 5 N/C Reserved
8 27 7 /Index 0=Index
10 25 9 N/C (/MOTEA) -/- (0=Motor Enable Drive 0)
12 23 11 /DRVSB Drive Select 1
14 21 13 N/C (/DRVSA) -/-(Drive Select 0)
16 19 15 /MOTEB 0=Motor Enable Drive 1
18 17 17 /DIR 0=Direction Select
20 15 19 /Step 0=Head Step
22 13 21 /WDATE Write Data
24 11 23 /WGATE Floppy Write Enable, 0=Write Gate
26 9 25 /TRK00 0=Track 00
28 7 27 /WPT 0=Write Protect
30 5 29 /RDATA Read Data
32 3 31 /SIDE1 0=Side 1 Select
34 1 (blue wire²) 33 /RDY (/DSKCHG) 0=Ready (1=Disk Change/0=Ready³)
n/a n/a 35 N/C Amstrad 6128plus only
All others (odd) All others (even) All others (even) GND Ground

¹: Assuming you are using a cable which is made to match the Shugart standard on the floppy side.
²: Original cables from Amstrad/Schneider had blue wires to mark pin 1 (which is pin 34 in Shugart standard).
³: Although it might look like it, /RDY and /DSKCHG are not compatible. The CPC expects the drive to become ready (=0) by itself, while the DSKCHG signal stays high until confirmation through the PC, so the drive will never become RDY.
^4: Due to the first signal being on pin 1, there is no pin left for the first wire of the floppy cable (usually red). You can just cut it off, it's just another GND.

Except for the hint in note 3, a PC floppy can be directly operated on this connector, as long as you keep attention to the fact that the red wire of a PC floppy cable which is unchanged on the floppy side belongs on pin 34 of the CPC connector. Some drives can be jumpered to output the desired /RDY signal, some can at least be soldered. Others can be operated by "tuning" the cable. See 3 1/2" & 5 1/4" Disk Drives for more detailed instructions, incl. Side Switch.

Aleste 520EX Disc Connector

The Aleste 520EX has (almost) the same 34 pin male card-edge as the CPC,

 A1..A17 Same as <odd> CPC Pins 33..1 (NC,NC,NC,/INDEX,etc)   A17 ------ A1
 B1..B17 Same as <even> CPC Pins 34..2 (all wired to GND)     B17 ------ B1

The drive select signals are a little different:

 CPC.Pin25=NC                      ALESTE.PinA5=DRIVE1 (B:)


Multiple Amstrad/Schneider peculiarities have to be kept in mind:

  • The numbering on the CPC664/non-German CPC6128 is exactly the opposite of that in the Shugart standard (Shugart 1 = CPC 34, Shugart 2 = CPC 33 and so on)
  • The German CPC6128 manual is a 1:1 copy of the Amstrad CPC6128 manual, although the Centronics connector would need to be mounted top-down in order for the plug numbering to match the pin numbering as shown in the manual, which it isn't. Thus, the pin numbers in the manual not only mismatch the Shugart standard, but also the plug. E.g.: Pin 1 on the pin out in the manual and in the table below will be numbered 36 on the plug and 34 according to the Shugart standard.
  • For a maximum confusion, Amstrad has completely changed the pin out numbering on the 6128plus. Here, the numbers on the connector were rotated in order to match those of the plug, but still they do not match the Shugart standard: Pin 1 on the 6128plus is wire 2 of a Shugart-compatible cable, so that wire 1 cannot be connected at all and all signals are shifted by one.

For these reasons it makes sense to forget about the numbering by Amstrad/Schneider completely.
Instead, only keep in mind where wire 1 of a proper Shugart cable belongs to, relative to a standard numbered plug, and use Shugart wire numbers when referring/looking to a specific signal.

Wire 1 (Red wire) orientation table

Wire No. (Shugart) CPC664/CPC6128 (& Schneider CPC6128 manual) Schneider CPC6128 actual plug 6128plus
1 (Red) 34 3 cut off
2 (Next to red) 33 4 1


Wire 1 (Red wire) orientation table, more descriptive

Wire No. (Shugart) CPC664/CPC6128 edge CPC6128 Centronics 6128plus Centronics
1 (Red) Vice-versa/Opposite from index nose Third from right/first One over right side/-1 from first