AXIOMATIC LIN - J1939 CAN, User Manual

Page: 39 / 82

UMAX140610. LIN
– J1939 CAN Protocol Converter with PWM Output. Version 1
Page: 39-81
3.5.1 Conditions Evaluation
The first step in determining which table will be selected as the active table is to first evaluate
the conditions associated with a given table. Each table has associated with it up to three
conditions that can be evaluated.
Argument Z is always a logical output from another function block. As always, the source is a
combination of the functional block type and number, setpoints
“Table X - Condition Y,
Argument 1 Source”
and
“Table X, Condition Y, Argument 1 Number”
, where both X = 1
to 3 and Y = 1 to 3.
The condition is evaluated based on the
“Table X, Condition Y Operator”
selected by the
user. It is always
‘=, Equal’
by default. The only way to change this is to have two valid
arguments selected for any given condition. Options for the operator are listed in the table
below.
Table 21. Condition Operator Options
Value Meaning
0 =, Equal
1 !=, Not Equal
2 >, Greater Than
3 >=, Greater Than or Equal
4 <, Less Than
5 <=, Less Than or Equal
For example, a condition for a transmission control shift selection, as shown in Figure 18 in the
previous section, could be that the Engine RPM received on CAN message 3 be less than a
certain value to select a Soft Fill profile. In this case,
“…Argument 1 Source”
would be set to
‘CAN Receive Message 3’, “…Argument 2 Source”
to
‘Constant Continuous Data 1
, and the
“…Operator”
to
‘<, Less Than.’
By default, both arguments are set to
‘Control Source Not Used’
which disables the condition,
and automatically results in a value of N/A as the result. Although Figure 20 shows only True
or False as a result of a condition evaluation, the reality is that there could be four possible
results, as described in the table below.
Table 22. Condition Evaluation Results
Value Meaning Reason
0 False (Argument 1) Operator (Argument 2) = False
1 True (Argument 1) Operator (Argument 2) = True
2 Error Argument 1 or 2 output was reported as being in an error state
3 Not Applicable Argument 1 or 2 is not available (i.e. set to
‘Control Source Not
Used’
)