Echelon FTXL - Manual (Page 173)

FTXL User’s Guide 161
Resource Number Notes
Events 10 Modify the number of events, if needed, within
the operating-system settings.
To calculate the maximum number of critical sections that are required for your
FTXL application, use the following formula:
[ ]
)) ( * 2 ( )) ( * 4 ( 50 uff AppOutputB ff AppInputBu CritSect + + =
where:
• CritSect is the number of critical sections required
• AppInputBuff is the number of application input buffers
• AppOutputBuff is the number of application output buffers, including
priority buffers and non-priority buffers
You specify the number of application buffers on the Buffer Configuration page of
the LonTalk Interface Developer utility.
Table 31 lists the default values for the number of application buffers and the
number of critical sections defined within the FTXL OSAL.
Table 31. Default Number of Buffers and Critical Sections
Buffer Type Number Critical Sections
Application input 5 20
Application output, non-
priority 5 10
Application output,
priority 1 2
Thus, using the formula, the default number of critical sections is 82:
50 + 20 + 10 + 2 = 82
You can modify the number of critical sections defined for the application within
the settings for the operating system, but the number should not be less than the
default number calculated according to the formula.
Specifying Task Priorities
An FTXL application program must include at least one application task (or
thread), but can include additional tasks (or threads). When assigning task
priorities, you must assign application task priorities so that they do not conflict
with the required priorties for the tasks defined for the FTXL LonTalk protocol
stack. In addition, some operating systems, such as the Micrium μC/OS-II
operating system, require that each task be assigned a unique priority.
The FTXL OSAL defines three abstract priorties: high, medium, and low, as
shown in Figure 13 on page 162.