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

GMW3110 
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February 2010 
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Prefix for Hexadecimal Number 
b 
Suffix for Binary Number 
/* 
Prefix for a Comment String 
*/ 
Suffix for comment string of more than one line 
3.6.2 Pseudo Code Definition. 
The ECU Interface functions are presented in pseudo code format. This is to 
reduce the possibility of multiple interpretations of a diagnostic service (test mode). The indentation practices 
in the example functions below shall be followed to enhance readability. 
3.6.2.1 Pseudo Code Syntax. 
3.6.2.1.1 Decision Statement. 
Decision statements use the keywords IF, THEN, ELSE, ELSE IF and ENDIF 
to control the flow of execution. Included in the parenthesis is a relational expression which can be evaluated 
as either TRUE or FALSE. The flow of execution through decision statements is based on the results of the 
evaluation of the relational expression(s) contained within them. An example is provided below: 
IF (relational expression #1) THEN 
body when expression #1 is TRUE 
ELSE IF (relational expression #2) THEN 
body when expression #2 is TRUE 
ELSE 
body when expressions #1 and #2 are FALSE 
ENDIF 
Note:
Every IF statement shall have a corresponding ELSE, ELSE IF, or ENDIF statement. Below is an 
example of pseudo code which uses two variables x and y. 
IF (x > y) THEN x = x+2 /* body when x > y */ 
ELSE IF (x = y) THEN 
IF (x!= 0) 
/* body when x = y */ 
x = y/x 
/* body when x = y and also body when x!= 0 */ 
ENDIF 
/* body when x = y */ 
ELSE 
x = x*y 
/* body when x < y */ 
ENDIF 
3.6.2.1.2 Select Statement.
Select statements are useful when a different body of code is to execute based 
on a series of relational expressions. The select statement uses the keywords SELECT FIRST and 
ENDSELECT to mark the beginning and ending of the select statement. When this statement is encountered, 
the relational expression in parenthesis next to the first WHEN keyword is evaluated. If this relational 
expression evaluates TRUE, then the body after the first WHEN keyword is executed. The body portion is 
indented one level and ends at the last line before the next WHEN keyword. If the first relational expression 
evaluates FALSE, the relational expression after the next WHEN keyword is evaluated. If this relational 
expression evaluates TRUE, then the body associated with that WHEN keyword is executed. If none of the 
relational expressions following WHEN keywords evaluate to TRUE, then the body following the OTHERWISE 
keyword is executed. After executing the body section of code following any WHEN or OTHERWISE keyword, 
the select statement is exited and the code begins executing after the ENDSELECT keyword. An example of 
this type of statement is included below: 
SELECT FIRST 
WHEN (first relational expression)
body when first expression is TRUE 
WHEN (second relational expression) 
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