Discovery mode (Addressing DaisyChain)

 

The Discovery-Mode executes the addressing of the connected sensors, if they have no predefined address and are connected in daisy chain wiring.

Each sensor needs a unique 4-bit address (A3:A0).
The address 0 is dreserved for global commands (broadcast), which are for all sensors at the same time.

 

info_green.jpg

The activiation of the Discovery-Modes is done by according commands of the ECU. The commands are sensor specified and have to be taken from the data sheet of the manufacturer and be entered at the master data editor.

A3

A2

A1

A0

 Sensor

0

0

0

0

 All sensors (broadcast)

0

0

0

1

 Sensor 1

0

0

1

0

 Sensor 2

0

0

1

1

 Sensor 3

0

1

0

0

 Sensor 4

0

1

0

1

 Sensor 5

0

1

1

0

 Sensor 6

0

1

1

1

 Sensor 7

1

0

0

0

 Sensor 8

1

0

0

1

 Sensor 9

1

0

1

0

 Sensor 10

1

0

1

1

 Sensor 11

1

1

0

0

 Sensor 12

1

1

0

1

 Sensor 13

1

1

1

0

 Sensor 14

1

1

1

1

 Sensor 15

 

Example of changing the operation mode at the sensor data window

 

Procedure of the DiscoveryMode:

 

  1. Switch on the bus supply voltage by the master.
  2. Transmission of the DiscoveryMode command of the master (Logical 0 =  from VHigh/ VLow/VHigh-impulse)
  3. After a defined delay time, all connected sensors create a current ramp up to the double of their response current.
  4. Each sensor scans and compares the measurable current of the bus line.
    Thereby 3 possibilities are existing within the defined accept time (t    DiscAccept):
    -     The measurable current value is the same or more than the response current value (IResp):The sensor switch off its current and increase its address counter.
    -     The measurable current value is less than the response current value (IResp): The sensor continue its current ramp.
    -     No current value is measurable. The sensor accept the address 1 and switch off its current.
  5. After a predefined time period (tDisc_Per) the master send again a discovery mode command.
  6. Step 3 and 4 will be repeated.
  7. Step 5 will be repeated as much times as sensor exists.

 

 

16_discovery.jpg