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

9.3.2.3 Boot Software Description and Requirements. 
All SPS programmable ECUs that support 
programming of the operational software shall contain boot software in a boot memory region. ECUs that 
support boot software shall continue to execute out of the boot until a complete set of Operational software and 
calibrations are programmed. 
The boot memory shall be protected against inadvertent erasure such that a failed attempt to modify program 
calibrations or operational software does not prohibit the ability of the ECU to recover and be programmed 
after the failed attempt. The ECU shall be able to recover and be reprogrammed if any of the following error 
conditions occur during the programming process. 
1. Loss of supplied power connection. 
2. Loss of the ground connection. 
3. Disruption of GMLAN communication. 
4. Over or under voltage conditions. 
Boot software resides in the boot memory region and is the software that an ECU begins executing upon 
powerup. Transfer of program control to the boot software also occurs once the ECU is informed that it is 
about to be programmed (refer to the $34 service). All SPS Programmable ECUs operating out of Boot 
memory shall not transmit any normal communication messages or any unsolicited diagnostic messages. 
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GM WORLDWIDE ENGINEERING STANDARDS 
GMW3110 
© Copyright 2010 General Motors All Rights Reserved 
February 2010 
Page 252 of 336 
The boot software can be broken down into the following components: Power Management, System 
Initialization, Message Handler, Programming Executive/Program Loader, Diagnostic Service Manager, and 
Programming Routines. See Figure 36. 
Figure 36: GMLAN Boot Software 
9.3.2.3.1 Boot Software Power Management. 
The power management portion of the boot software handles 
the wake-up mechanism supported by the ECU (if applicable). The wake-up mechanism for SWCAN ECUs is 
defined in GMW3104. Dual Wire CAN (DWCAN) ECUs that support a wake-up mechanism must document the 
mechanism used in the CTS. 
The power management component of the boot software also interfaces with the programming executive. If the 
programming executive does not detect the start of a programming event within 1 minute of the receipt of a 
wake-up, then the programming executive shall inform the power management logic which in turn shall cause 
the ECU to enter the low power state. 
The start of a programming event is defined to be the point where the programming_mode_active flag is set to 
YES. Refer to paragraph 8.17.6.2 (service $A5 pseudo code) for additional details. Once the programming 
event has started, the ECU shall remain awake until the programming event concludes (via the receipt of the 
$20 service or a P3
C
timeout). The ECU shall perform a software reset at the conclusion of the programming 
event.