Low Speed GMLAN Block Diagram

Fig 1: Low Speed GMLAN Block Diagram

Courtesy of GENERAL MOTORS COMPANY

Callout	Component Name
DA	Serial Data
DA	Serial Data
DA	Serial Data
DA	Serial Data
DA	Serial Data
DA	Serial Data
DA	Serial Data
DA	Serial Data
DA	Serial Data
DA	Serial Data
DA	Serial Data
DA	Serial Data
K9	K9 Body Control Module
K36	K36 Inflatable Restraint Sensing and Diagnostic Module
K60	K60 Steering Column Lock Module
P16	P16 Instrument Cluster
X84	X84 Data Link Connector
A11	A11 Radio
K33	K33 HVAC Control Module
T11	T11 Multimedia Player Interface Module
K73	K73 Telematics Communication Interface Control Module
K41R	K41R Rear Parking Assist Control Module
K84	K84 Keyless Entry Control Module
K85	Passenger Presence Module
K29	K29 Seat Heating Control Module

Low Speed GMLAN Bus is used in applications where a high data rate is not required which allows for the use of less complex components. It is typically used for operator controlled functions where the response time requirements are slower than those required for dynamic vehicle control.

The Low Speed GMLAN Serial Data Network consists of a single wire, ground referenced bus with high side voltage drive. During on road vehicle operation data symbols (1's and 0's) are transmitted sequentially at the normal rate of 33.3 Kbit/s. For component programming only, a special high speed data mode of 83.3 Kbit/s may be used.

Unlike the high speed dual wire networks, the single wire low speed network does not use terminating resistors at either end of the network.

The data symbols to be transmitted over the bus are represented by different voltage signals on the bus. When the Low Speed GMLAN Bus is at rest and is not being driven, there is a low signal voltage of approximately 0.2 V. This represents a logic "1". When a logic "0" is to be transmitted, the signal voltage is driven higher to around 4.0 V or higher.