SAAB WIS ONLINE

Brief description

Brief description

General

The bus is divided into a:


- P-bus (Powertrain bus)

- I-bus (Instrument bus)


A control module sends a message by sending ones and zeros in a predefined order. The control module only sends a message if no other control module is presently sending. The meaning of the combinations of ones and zeros is predefined so that all the control modules can interpret the information in the same way. The message contains information about what is being sent and the value, for example ”Coolant temperature" 100°C or ”A/C ON".


The data link connector can access both the P-bus and the I-bus. With an adapter, Tech2 can be connected to the data link connector and can communicate with the different control modules on the P-bus and I-bus.

Certain information sent by a control module is made available to all other bus control modules. The CIM relays information between the I-bus and P-bus.

P-bus and I-bus

The P-bus and I-bus are connected to the CIM and MIU. The buses are electrically isolated. The P-bus has a data transfer rate of 500 kbits/s and the I-bus of 33 kbits/s. The data rate on the P-bus is high to allow the powertrain systems access to information with the shortest possible delay, for example during air mass compensation when the selector lever is moved from N to D or torque limitation during gear changes.

Information on the P-bus is transferred between control modules on two leads: bus + (blue lead) and bus - (white lead). The leads are twisted to reduce their sensitivity against electrical interference. The I-bus only has one lead.