Bus communication
| Bus communication |
| P-bus and I-bus |
All the control modules in the Saab 9-5 are connected to the bus, with the exception of those for the ABS and SRS.
The buses are divided into the Powertrain bus (P-bus) and the Instrument bus (I-bus). Both buses are connected to the main instrument unit (MIU). The buses are electrically isolated from each other.
The data transfer rate on the P-bus is ten times faster than on the I-bus.
All the information sent from one control module is accessible to all the other control modules on the bus. The MIU is responsible for ensuring that information available on one bus is also available on the other bus.
The control unit sends out information on the bus at regular intervals. The interval between two transmissions depends on the type of information being transmitted and varies between 10 milliseconds (0.010 seconds) and one second. Information is also transmitted by the control module whenever the information changes.
Information is transferred between control modules via two leads, BUS+ (green lead) and BUS- (white lead). On the P-bus, the leads are twisted to reduce their sensitivity to electrical interference.
| The main unit uses the following information |
|
Information
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Values
|
From
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The value depends on the following sensor input, signal or function
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|
Ignition +B
|
ON/OFF
|
DICE
|
The main unit uses the +B information only as logic voltage.
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Key correct
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-
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TWICE
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The main unit uses the information for the theft protection function of the audio system.
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CD changer information
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Current settings
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CDC
|
Information on current CD and its location.
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Vehicle speed
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kph, mph
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MIU
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The main unit uses the information for the “speed-dependent volume” function.
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Steering wheel switches
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Seek >>, Seek <<,Vol +, Vol -, NXT, SRC
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SID
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The main unit uses the information to control the function (execute the command) selected via the steering wheel switches.
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Rheostat level
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0-100%
|
SID
|
The main unit uses the information to control the light intensity on the front display of the main unit.
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Rheostat Night Panel
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0-100%
|
SID
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The main unit uses the information to control the light intensity on the front display of the main unit.
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Night Panel
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ON/OFF
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SID
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The main unit uses the information to switch the “Night Panel” function on and off. When switched on, the light intensity on the main unit front display is reduced.
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Display lighting
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0-100%
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SID
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The main unit uses the information to control the light intensity on the front display of the main unit.
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Diagnostics communication
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|
DICE
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For further information on the bus, see Bus and Diagnostics Communication.
|
| The main unit transmits the following information |
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Information
|
Values
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Used by
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The value depends on the following sensor input, signal or function
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RDS time
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Hours, Minutes, Seconds
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SID
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SID uses the information for the time function (the clock).
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RDS day
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0-31
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SID
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SID uses the information for the time function (the clock).
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RDS month
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January - December
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SID
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SID uses the information for the time function (the clock).
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Sound
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Sound information
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SID
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SID uses the information to activate the type of sound requested from the main unit.
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Text message
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Text information
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SID
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SID uses the information to show on the display the setting of the source currently in use.
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CD changer control
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Information for controlling the CD changer
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CDC
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The CD changer uses the information from the main unit to control the function selected on the CD changer.
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Diagnostics communication
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-
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DICE
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For further information on the bus, see Bus and Diagnostics Communication.
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