DeviceNet Master Protocol API

DeviceNet-Master Fundamentals • 17
2 Fundamentals
2.1 General Access Mechanisms on netX Systems
This chapter explains the possible ways to access a Protocol Stack running on a netX system :
1. By accessing the Dual Port Memory Interface directly or via a driver.
2. By accessing the Dual Port Memory Interface via a shared memory.
3. By interfacing with the Stack Task of the Protocol Stack.
The picture below visualizes these three ways:
1
2
(Extended) Status Block Send Mailbox Reveive Mailbox Output Data Image Input Data Image
AP Task
3
Fieldbus Task(s)
Network Abstraction Layer
Network
Figure 1 - The three different Ways to access a Protocol Stack running on a netX System
This chapter explains how to program the stack (alternative 3) correctly while the next chapter
describes accessing the protocol stack via the dual-port memory interface according to alternative 1
(and 2, if the user application is executed on the netX chip in the context of the rcX operating system
and uses the shared DPM). Finally, chapter 5 titled “The DeviceNet Application Interface” describes
the entire interface to the protocol stack in detail.
Depending on whether you choose the stack-oriented approach or the Dual Port Memory-based
approach, you will need either the information given in this chapter or those of the next chapter to be
able to work with the set of functions described in chapter 5. All of those functions use the four
parameters ulDest, ulSrc, ulDestId and ulSrcId. This chapter and the next one inform
about how to work with these important parameters.
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Edition 3 – API:DeviceNet-Master#EN– 2009/01