GF54.21-P-4170TX Central Gateway Control Unit, Component Description

GF54.21-P-4170TX Central gateway control unit, component description

Component Identification:

Location
The central gateway control unit (N93) (CGW) is in the cockpit on the left-hand side (relative to the direction of travel) next to the A-pillar.

task
The tasks of the CGW are:
^ Global variant coding
^ Specific variant coding
^ Data interface (gateway) between Controller Area Network bus class B (interior) (CAN-B) and Controller Area Network bus class C (engine compartment) (CAN-C)
^ Supports flow of information destined for transmission from CAN B to the diagnosis bus
^ Supports flow of information from the diagnosis bus to CAN B
^ Supports flow of information destined for transmission from CAN C to the diagnosis bus
^ Supports flow of information destined for transmission from CAN C to the diagnosis bus
^ Service processor (Active Service System PLUS (ASSYST PLUS))
^ Maintenance interval display (Active Service System (ASSYST))

The CGW forwards global information such as model series and national version to the control units via CAN-B and CAN-C. This data is then transferred to the Controller Area Network (Data bus/CAN bus) (CAN) at period intervals.

During normal vehicle operation, information which is available on one CAN and required to support operation of control units on another CAN is transmitted by the CGW.

Diagnosis bus
The primary purpose of the diagnosis bus is to allow connection of an external tester. The tester is then used to diagnose the control units in the diagnosis mode.

Data transfer rates in the bus systems
The bus systems at the CGW have the following data transfer rates:
^ Diagnosis bus: 500 kbit/s
^ CAN-B: 83.3 kbit/s
^ CAN-C: 500 kbit/s

Interface (gateway) function
A distinction is made between 2 types of gateway function:
^ When the external tester is connected to the system in its diagnosis mode, the tester's diagnostic data requests are transmitted to the diagnosis bus for subsequent forwarding to the CGW. The CGW then sends the diagnostic data requests to the appropriate control units of CAN-B or CAN-C. Conversely, the diagnostic reply messages are sent from the control units of CAN-B or CAN-C to the CGW. The CGW then transmits these diagnostic reply messages to the diagnosis bus. The tester accesses these answers on the diagnosis bus. This interface functionality is embodied in the term diagnosis gateway.
^ During normal vehicle operation, information which is available on CAN-B and required to support operation of control units on CAN-C is forwarded by the CGW. Conversely, information which is available on CAN-C and required to support operation of control units on CAN-B is forwarded by the CGW. This interface function is defined as the functional gateway.

In the functional gateway the entire CAN message can be transferred from the source bus to the target bus, or, alternatively, only specific data from within the CAN message will be transferred from the source bus to the target bus. If only specific data from the CAN message is transferred from the source bus to the destination bus, the CGW generates a new CAN message and sends it to the destination bus.

Gateway functionality is available only when the respective destination bus is active.