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SCIOPTA - Real-Time Kernel

6-8 Manual Version 4.1 User’s Manual

SCIOPTA - Real-Time Kernel

6 Messages

6.9 Messages and Modules

A process can only allocate a message from a pool inside the same module.

Messages transmitted and received within a module

are not copied, only the pointer to the message is transferred.

Messages which are transmitted across modules boundaries are

always copied if the Inter-Module setting in the

system configuration utility is set to “always copy”. If it set to never copy, messages between modules are not cop-

ied (see chapter

16.9.1 “General System Configuration Tab” on page 16-8).

A module can be declared as friend of

another module. The message which was transmitted from the module to its

declared friend will not be copied. But in return if the friend sends back a message it will be copied. To avoid this

the receiver needs to declare the sender also as friend.

To copy such a message the kernel will

allocate a buffer from the default pool of the module where the receiving

process resides. It must be guaranteed that there is a big enough buffer in the receiving module available to fit the

message.

Figure 6-7: SCIOPTA Messages and Modules

System Module

Pool

Process

Module

Pool

Process

Module

Pool

Process

Pool

MMU Segment A MMU Segment B

1 2 ... 61 62 63 64 65 66 67 68 69 70 71 ... 225 226

CompuLab SBC-X270 Manual de usuario Pagina 66