MDD to M48, Speed not displaying

[prcvl]

I've recently picked up a reconditioned MDD to use with my M48.
Comms works, and the MDD is displaying *almost* everything.
On the main display, engine RPM and gear display correctly, but Speed always remains 0.
If I go to Tuning mode, I can toggle through to the screen where Digital 1 is displayed, and the speed is displayed correctly.
I only have one vehicle speed sensor, on digital input 1. (Digital input 2 is used for logging enable switch)
Apart from logging it, i do not use vehicle speed for traction or launch control (both enabled).
How do i get the Speed to display on the main screen? The manual does not state that the vehicle speed needs to be on any specific pin.
Since the Gear is being calculated correctly, why doesn't the speed display?
A bit frustrating, as Motec documentation is usually very good. Any hints what is wrong?

[prcvl]

Solved!
For anyone else who ever has this problem with an old ECU, you need to go to:
Misc Functions > Traction Control > Function
Set Function = 0 (Measure slip - no control)
Set Parameter SLIP SOURCE = 1 or 2
...depending which digital IO the speedo pin is connected to.
i.e., My speedo signal is on digital input 1, so I need to set SLIP SOURCE = 1 (Rolling wheel on Digital input 1)
Now the speedo works on the MDD main screen.