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

GM WORLDWIDE ENGINEERING STANDARDS 
GMW3110 
© Copyright 2010 General Motors All Rights Reserved 
February 2010 
Page 254 of 336 
The programming executive may reside in boot memory or it may be contained within the routine section of the 
ECU utility file, downloaded into RAM, and then executed. The advantage of placing the programming 
executive in RAM is that it allows the boot to be smaller and it also allows updates to the programming 
executive without requiring a new hardware part. The disadvantage to this approach is a slight increase in 
programming time in order to transfer the programming executive to RAM via the serial data bus and begin its 
execution. If the programming executive is located in the utility file then a portion of the programming executive 
(called the program loader) remains in the boot memory. The program loader component gets program control 
from the boot software initialization component if some portion of the software or calibration data is not present 
in the ECU. The program loader interfaces with the power management component to allow an ECU to enter a 
low power state if no programming session has been established within 1 minute of a wake-up. The program 
loader also interfaces with the boot software diagnostic service manager and the boot software message 
handler in order to receive the download of the programming executive, and then transfer program control to 
the programming executive. If the programming executive resides in boot memory then the program loader 
and programming executive are considered as one component. See Figure 36. 
9.3.2.3.5 Boot Software Diagnostic Service Manager. 
The boot software diagnostic service manager 
contains the logic for handling diagnostic requests and responses during programming. The level of support of 
diagnostic services within the boot shall be minimized in order to keep the size of the boot software as small as 
possible. Refer to paragraph 9.3.2.4 for specific requirements on the implementation of diagnostic services 
within the boot software. 
The diagnostic service manager interfaces with the boot software programming executive which controls the 
sequence of events during programming.