Siemens SIMATIC NET SPC 4-2 LF, Руководство пользователя

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Memory Assignment
PROFIBUS Controller SPC 4®-2 LF
C79000-G8976-C157-3
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Caution
After initialization in the offline mode, both pointers must be set to the required start
of the range. THEY CANNOT BE MODIFIED DYNAMICALLY; in other words, to
modify the memory assignment, the SPC 4-2 must be changed to offline. A change
in the order of the pointers leads to an incorrect response of the SPC 4-2 related to
the individual memory areas.
If the SPC 4-2 receives request frames, it enters them in the indication queue. The
indication queue is organized as a ring buffer; in other words the data to be
processed is entered one after the other in the queue as long as there is still space
in the queue and blocks that have been processed are taken out of the queue. The
indication queue is organized using write and read pointers. The indication read
pointer (IND-RP) must be set by the FLC while the hardware of the SPC 4-2 is
responsible for updating the indication write pointer (IND-WP).
Since this is a ring buffer, the end of the queue must be monitored when data are
entered. If this is exceeded, the address must be wrapped. The SPC 4-2 provides
hardware support that automatically wraps the address.
Reply-on-Indication Blocks
The FLC must provide reply data in these buffers. The reply data are assigned to
the calls using pointers in the SAP lists.
Swap Buffers
To support PROFIBUS DP services (DP mode = 1 in the mode register 0), 6 swap
buffers must be provided.
Ident Buffer
The Ident buffer contains the reply data for Ident frames.
Node Table
The node table is required to filter SDN or DDB response frames.