The 8906 is a DIN-Rail-Mounted Interface block for connecting an 8601 Stepper Motor Controller Industry Pack or an 8513 Quadrature Encoder Input Industry Pack to the external system.

The unit has one 50-way SCSI-II connector for the cable to the host VME64x system (using a straight-through transition board) and four 15-way Cannon D-type sockets, one for each motor, plus a 25-way Cannon D-type socket for auxiliary signals. The unit is modelled on the OMS interface unit for the VME58 motor controller card.

 The actual signals handled are as follows:

 For each Motor Channel:

Step Output                        SK1, 2, 3, 4         9
Direction Output                   SK1, 2, 3, 4         10
Aux Output 1                       SK1, 2, 3, 4         11
Encoder phase A                  SK1, 2, 3, 4         2/3
Encoder phase B                  SK1, 2, 3, 4         6/7
Encoder Index                     SK1, 2, 3, 4         4/5
Positive Limit Switch             SK1, 2, 3, 4         13
Negative Limit Switch           SK1, 2, 3, 4         14
Home Limit Switch                SK1, 2, 3, 4         15
Digital Ground                      SK1, 2, 3, 4         8
Analogue Ground                  SK1, 2, 3, 4         12
+ 5 volts power                    SK1, 2, 3, 4         1

 Note: the encoder signals are differential RS422 inputs, terminated into 100 ohms. 

The auxiliary connector carries the following signals: 

Signal                                               Pin Number(s)

Channel 1 Auxiliary output 2           15
Channel 2 Auxiliary output 2           16
Channel 3 Auxiliary output 2           18
Channel 4 Auxiliary output 2           19
Channel 1 Auxiliary input 1              2
Channel 2 Auxiliary input 1              3
Channel 3 Auxiliary input 1              5
Channel 4 Auxiliary input 1              6
Channel 1 Auxiliary input 2              9
Channel 2 Auxiliary input 2              21
Channel 3 Auxiliary input 2              10
Channel 4 Auxiliary input 2              22
Digital Ground                               1, 7, 8, 13, 14, 25.
+ 5 volts power                             4, 11, 17, 20, 23.

 Power supplies: The unit is provided with local 5 volts logic power via a screw terminal block. It uses this power on-board, sends it to the optical encoders and also uses it to drive the output signals, which expect to connect to opto-interface input stages, such as that used on the Parker OEM750 motor unit. This terminal block also carries a local earth connection. This is used by the protection system for the RS422 differential encoder inputs, where all signals have a varistor to earth. 

When used with the 8513 Quadrature input IP card, only the encoder inputs have any function. The unit then handles four encoders, each with differential phase A, phase B and index signals.