General Specification Electrical Function gmw3110 General Motors Local Area Network Enhanced Diagnostic Test Mode Specification

9.3.2.3.2 Boot Software System Initialization. 
The system initialization component of the boot software is 
responsible for ECU initialization upon powerup or after a reset. Tasks of this component include (but are not 
limited to) I/O initialization and determining if valid operational software and calibrations are present in the 
ECU. The system initialization software shall be able to determine if the ECU has only boot software present, 
boot software and operational software present, or if boot software, operational software and calibrations are 
all present. The exact method used to determine if valid operational software and calibrations are present must 
be documented in a CTS, GM provided bootloader specification or ECU specific diagnostic implementation 
specification. If valid operational software and calibrations are present, then the system initialization 
component completes its initialization and transfers control to the operational software. Otherwise, the ECU 
transfers program control to the boot software programming executive or program loader. 
If valid operational software and calibrations are not present, then the initialization component of the boot 
software shall initialize the ECU I/O in a manner that meets the requirements specified in paragraph 9.2. 
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GM WORLDWIDE ENGINEERING STANDARDS 
GMW3110 
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February 2010 
Page 253 of 336 
9.3.2.3.3 Boot Software Message Handler. 
The boot software message handler is responsible for 
transferring information between the programming tool and the boot software programming executive. Included 
in this component of the boot software are the CAN driver, the CAN hardware message filtering logic, support 
of the Network Transport Layer, and high speed support for SWCAN ECUs. 
The Network Layer supported in the ECU boot software shall maximize the size of the network layer buffer and 
minimize the size of the network layer parameter ST
min
to maximize the efficiency of data block transfers. The 
ECU shall allocate some or all of its RAM resources used for normal operation for the network layer buffer 
when operating out of the boot code. The value of ST
min
during normal operation can be different than the 
value used during programming. 
The CAN hardware message filtering logic in the boot software shall meet the requirements specified in 
paragraph 9.2 - Requirements for All ECUs to Support Programming.