Features Of Pointer-Based Communications - Siemens SIMATIC FM 458-1 DP User Manual

Access to the I/O
area (P bus) for FM
458-1 DP
Saving data in a
data block

4.5.3 Features of pointer-based communications

For all platforms
and interfaces of
the SIMATIC
control systems
Application Module FM 458-1 DP - User Manual
A5E01078222-02 Edition 03.2009
128 bytes can be transferred from the FM 458-1 DP to the S7-CPU in
each direction via the I/O area of the P bus.
Using the new S7RD_P/S7WR_P blocks, all 128 bytes can be copied
into a buffer using a block and that with an optimized computation time.
This buffer can then be accessed flexibly using read/write blocks via the
pointer interface. Indexed access is also possible
Sub-areas can also be accessed using offset and length data.
Data can be saved in a data memory which can be universally used. This
data memory can then be accessed using read/write blocks via a pointer
interface. Several similar buffers can be set-up in this data block. This
means, for example, that recipes can be easily saved and called-up.
 When generating CFC charts, the configuring time and costs are
reduced,
especially if very many virtual connections had to be generated.
 Connections to the telegram data can be newly inserted and changed
online (pointer, buffer offset).
 Communication connections can be copied with or within chart blocks
and centrally changed with them. This means that it is especially
simple and quickly to configure, for example, similar communication
links to a large number of drives.
 Telegram buffer data can be accessed indexed using 2 offset data.
This means that extremely simple modular programs (e.g. chart
blocks) can be generated and used.
 Larger data quantities can be transparently processed (e.g.
blockwise) (copied), e.g. using the copy block CPY_P in data block
DB_P.
 For FM 458-1 DP:
 using "B-Receive" (BRCV) high quantities of data can be
transferred from the S7-CPU to the FM 458-1 DP via the K bus.
 128 bytes can be simply configured and quickly transferred with
low computation overhead via the I/O area of the P bus.
 A special read/write block is available for every data type (BYTE, INT,
DINT, REAL).
 Before accessing REAL data, the type is checked.
 These configuring possibilities can be principally used for all of the
SIMATIC control system platforms. This means FM 458-1 DP,
SIMATIC TDC, T400 and SIMADYN D. The reason for this is that
block processing is independent of the subordinate (secondary)
hardware.
Configuring
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