MITTENTITEL

Timings und voltages, nominal and real.

The values you find in the text arereal world measurements. So thee might be slight differences between my measurements and what you fin when you do tests on your system.

A real world value of 102 ms might be nominal (meant to be) 100 ms.


LSB und MSB

We are used to numbers where the most significant digit is to the left. That is calld MSB order.

LSB is just the opposite. The most significant digit is to the right.

So MSB ordered 101110 is eqivalent to LSB ordered 011101.

 

Physical layer

The D132 System is a two rail system just as all other current slot car systems.

With an analog system the voltage betwee both rails is varied and the voltage change results in a rpm change of the motor and that in a speed change.

Digital systems use a constant voltage between the rails, D132 uses 14.8V. I will call it 15V throughout the text because it's simpler and still close enough.

As the voltage is not available as a control method for the speed, the cars mut be informed in a different way.

And that different way, are data packets that are sent over the same two rails, which are used to supply the energy for the cars.

To transmit the data packets the 15V line ist switched on and off in a certain rhythm comparable to a morse code.

On the D132 system it looks like this:

Every 7.5 ms there is a new data word. There are ten different data words which are constiniously repeated. So each data word is repeated every 75ms. That's eqivalent to a frequency of 13 Hz.

Each data word is a serial data word encoded using the Manchaster code. The data rate is nominally 10 kBaud, that's 100µs per bit.

When using Manchester codeing, the level before the "counting" slope decides the bit value.

The first bit is always a start bit.

The number of data bits varies. There are data words with 7, 9 and 12 data bits.

There is no dedicated stopbit.

Without any obvious reason there are data word which use MSB and some which use LSB order.

Semantic layer

There are ten different data words which form a cycle which is endlessly repeated.

Six of them have the same structure. Each of them transmits the information of one controller to the respective car.

Ususally the data words are transmitted in the following order:

  • Programword
  • PaceAndGhostCarword
  • Activityword
  • Controllerword 0
  • Controllerword 4
  • Controllerword 1
  • Controllerword 5
  • Controllerword 2
  • Activityword
  • Controllerword 3

Controllerword: 1 C2 C1 C0 LC S3 S2 S1 S0 FU
The controllerword tells the cars which car should go how fast whether to change lanes and whether to use fuel management. Packets for all possible controllers are sent even for those controllers not connected.

1 Startbit
C2 C1 C0 Controller id (0-5). MSB
LC

Lane change button. 0 when the button is pressed.
S3 S2 S1 S0

Speed (0-15) MSB
FU When 1 the cars have to use fuel management.

PaceAndGhostCarword: 1 1 1 1 STOP CK GO PIT PC FU
On the first look it seems to be the controllerword for car number 7, but the data word is used for controlling ghost- and pace cars..

1 Startbit
1 1 1 Controller id (7). MSB
STOP

If the Bit is 1, the Ghost- and Pacecars are not allowed to run. This is used before a race starts and when the starting lights are active.
CK

A clock signal. This bit changes every time the data word is sent.

GO The inversion of stop.
PIT When the pace car button has been pressed, this bit shows that the pace car is to return to the pit stop lane. When this bit is 0 the pace car is to return on a 1 it has to go on circling. When the pace car is not activated, the bit is set to 0.
PC This bit is 1 as long as the pacecar is activated after the pace car button has been pressed.
FU 1, if the fuel management is activated.

Aktivityword: 1 C0 C1 C2 C3 C4 C5 ANY
This data word shows on which controllers the throttles are pressed. his is throttle only the lane change button does not come into it. This word is sent twice in every cycle.

1 Startbit
C0 This bit is 1, when the throttle of controller 0 is pressed.
C1 This bit is 2, when the throttle of controller 0 is pressed.
C2 C3 C4 C5

the same procedure just for controllers 2 to 5.
ANY This bit is 1, when the throttle of at least one controller is pressed.

Programword: 1 V0 V1 V2 V3 P0 P1 P2 0 0 C0 C1 C2
That word is used to inform early starters and to prgram maximum speed, maximum break leve and maximum fuel level. When programming each word is sent twice.

When there is an early start the id of the culprit is transmitted by this data word as well. C0 to C2 will hold the car id, P0-P2 will have a value of 4 (no programming) and the value (V0-V3) will be 9. Only the first car starting early is reported.

1 Startbit
V0 V1 V2 V3 Value (0-15) the selected parameter shall be set to. LSB
P0 P1 P2

Parameter:

000 Speed (0)
100 Brake (1)
010 Fuel (2)
001 No programming (4)
0 0

Zeroes
C0 C1 C2 Id of affected car (0-7). LSB