 RQDX1 Controller Module Cable signals.

              J1 Connector Signals
J1 Pin                Signal name
1             MFMWRTDT1 (H) (RD51 only signal)
2             MFMWRTDT1 (L)           "
3             GROUND
4             HEAD SEL 2 (L) (RDXX ONLY SIGNAL) (reserved for future use)
5             GROUND
6             SEEKCPLT (L) (RD51 ONLY SIGNAL)
7             RD1 RDY (H) (RD51 ONLY SIGNAL)
8             WRT FAULT (L)
9             DRVBUSOE (L)

10            HEAD SEL 1 (L) (RD51 ONLY SIGNAL)
11            RX0WPTLED (L) (RX50 ONLY SIGNAL)
12            RD0 RDY (H) (RD51)
13            RX1WPTLED (L) (RX50)
14            RDVSL0ACK (L) (RD51)
15            MFMRDDAT0 (H) (RD51)
16            MFMRDDAT0 (L) (RD51)
17            MFMWRTDT0 (H) (RD51)
18            MFMWRTDT0 (L) (RD51)
19            MFMRDDAT1 (H) (RD51)

20            MFMRDDAT1 (L) (RD51)
21            GROUND
22            REDUCWRTI (L)
23            RD0WRTPRO (L) (RD51)
24            DRV SEL 4 (L)
25            GROUND
26            INDEX (L)
27            RD1WRTPRO (L) (RD51)
28            DRV SEL 1 (L)
29            DRV SEL 2 (L)

30            DRV SEL 3 (L)
31            RX2WPTLED (L) (RX50)
32            RXMOTORON (L) (RX50)
33            GROUND
34            DIRECTION (L)
35            GROUND
36            STEP (L)
37            GROUND
38            RXWRTDATA (L) (RX50)
39            GROUND

40            WRT GATE (L)
41            GROUND
42            TRACK 00 (L)
43            RX3WPTLED (L) (RX50)
44            DRVSL1ACK (L) (RD51)
45            GROUND
46            READ DATA (L) (RX50)
47            GROUND
48            HEAD SEL 0 (L)
49            GROUND
50            READY (L)



  RD51 disk drive connector pin assignments

GND return pin        Signal pin      Signal name
      1               2       Reserved
      3               4       Head Select 2
      5               6       Write gate
      7               8       Seek complete
      9               10      Track 0
      11              12      Write Fault
      13              14      Head select 0
      15              16      Reserved (to J2 pin 7)
      17              18      Head select 1
      19              20      Index
      21              22      Ready
      23              24      Step
      25              26      Drive select 1
      27              28           "       2
      29              30           "       3
      31              32           "       4
      33              34      Direction In



 RD51 disk drive J2 signal Connector pin assignments

GND return pin        Signal pin      Signal name
      2               1       Drive selected
      4               3       Reserved
      6               5           "
      8               7           "    (to J1 pin 16)
              9,10            Reserved
      12              11      GND
                      13      +MFM write data
                      14      -MFM write data
      16              15      GND
                      17      +MFM read data
                      18      -MFM read data
      20              19      GND

Table C3.  RD51 disk drive J3 Power connector pin assignments

GND return pin        Signal pin      Signal name
      2               1       +12 V
      3               4       +5 V





From: Steve Mitchell <grian!seabhag!steve@elroy.Jpl.Nasa.Gov>

I can't help a whole lot with the pin-out for the RD interface, except
to say that they're standard MFM ST-506 interfaced drives.  In fact,
the RD51 _IS_ an ST-506 drive.  You should be able to get the actual
pin-outs from PClone hardware books.  The 20 pin cable is the data
cable, which runs direct from the controller to the drive (star
topology).  The 34 pin cable is the control cable, which is usually
daisy-chained to all the drives attached to a given controller.  In
both cases, most designers just use straight ribbon cables.

For the RX-50 cable, I may be a little more help.  My (limited)
understanding is that the RX-50 drive interface is the standard floppy
drive interface.  If that is the case, referring back to the
documentation for my ancient Heathkit H-89 computer (back in the days
when when men were men and you got schematics for almost everything)
we find:

all odd pins ground
2             not connected
4             not connected
6             Drive select 0 (or 4 on some drives)
8             INDEXN
10            Drive select 1
12            Drive select 2
14            Drive select 3
16            MOTOR
18            DIR
20            STEP
22            CWD (Write data)
24            WG (Write gate)
26            TK0N (Track 0)
28            WPN (write protect)
30            RRN (Read data)
32            SIDEN
34            not connected

Multiple floppies are daisy-chained on the same 34 pin cable.  Like
the hard drive cables, almost everyone uses straight ribbon cables
between the controller and the drives.  The only exception to this is
IBM and the PClones, which for the floppy cable (and the hard drive
control cable in many cases) use a ribbon with just a few lines of the
ribbon twisted at the connector in the middle of the cable.  This is
used to force the drive selection (end of cable is Drive0, middle
connector is Drive1).  This of course means you DO NOT use the Drive
Select jumpers/switches on the floppies on one of these perverse,
twisted cables.  sigh.

