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AMX System Configuration
14.4 System Parameter Definition
The System Parameter window allows you to define the general operating parameters of
your AMX system. The layout of the window is shown in Figure 14.3-1 in Chapter 14.3.
Kernel Options
AMX Message Envelopes
AMX passes a message to a mailbox or message exchange in a message envelope. The
application parameters which form the message are copied into the envelope and added to
the task mailbox or message exchange.
The number of message envelopes required by your application must be defined. The
upper limit of the maximum number of envelopes is established by the fact that all
message envelopes must reside in one segment which is limited to 64K bytes. For each
of these message envelopes, the Builder will allocate storage for private AMX use.
Unfortunately, no hard and fast rule can be provided to determine the number of message
envelopes needed. For simple systems with little message queuing and few tasks
executing concurrently, the number of required message envelopes can range from one to
twice the number of tasks in the system. More complex systems with significant queuing
requirements may require many more envelopes.
AMX Message Size
The maximum size of the message to be passed in a message envelope must also be
defined by you. The minimum message size is 12 bytes. The message size must be a
multiple of 4.
AMX Kernel Stack Size
The AMX Kernel Task requires a minimum stack size of 128 bytes. In addition to this
minimum, you must allocate sufficient stack to satisfy the worst case requirements of all
application Restart Procedures and Timer Procedures. If you have any nonconforming
ISPs, you must increase the Kernel Stack size to meet the interrupt overhead expected.
No increase is needed if the ISP uses fewer than 40 bytes of stack. The stack siz e must
be a multiple of 4 bytes.