Siemens SIMADYN D Manual page 241

Communications configuring
Overview of the 3 data transfer types, FM 458 ←→ SIMATIC-CPU
3.16.1
Designation Number of data
4 bytes to
1.
SIMATIC-CPU
Process interrupt
2. 128 bytes in the
send and 128
Data transfer with
bytes in the receive
I/O (peripheral)
direction
accesses
3. For extremely high
quantities of data:
Transferring data
sets/blocks max. approx. 125
data sets with each
max. 240 bytes
(refer below.)
Table 3-59 Data transfer, SIMATIC-CPU
3-152
Configuring
FM 458:
Block PAS7
SIMATIC-CPU:
OB40, etc.
FM 458:
blocks S7RD,
S7WR
SIMATIC-CPU:
transfer commands
for the I/O
(periphery)
FM 458:
"virtual
connections"
with blocks
@CPB, CRV/CTV
SIMATIC-CPU:
system functions
SFC58/59
Consistency:
All of the data
associated with a
telegram are
consistent with one
another, i.e. they
are transferred in a
"data package".
↔ FM 458
All of the 3 data transfer types can be used in parallel.
Speed
When PAS7 is
called, an interrupt
is initiated on the
SIMATIC CPU,
e.g. OB40
(if a higher priority
interrupt isn't being
processed at
precisely that
time).
When a block is
called, data is
immediately read-
out of the memory
or written into the
memory.
The data
associated with a
telegram are read
or sent when the
block is called.
System- and communication configuring D7-SYS - SIMADYN D
Computation time
(on the FM 458)
Extremely low:
only for PAS7
Computation times
of all configured
S7RD/S7WR
blocks:
each approx. 5µs.
Computation time
is required for each
data set via
telegram
processing
(approx. 30µs each
CRV/CTV) and to
copy the net data
into/out of the P-
bus memory.
If extremely large
data quantities are
involved and there
is a P-bus
utilization, then a
somewhat higher
degree of
computation time
can be assumed.
The data are
transferred into the
memory in blocks
up to max. 16
bytes. The P bus
must be re-
assigned between
the blocks, which
means that the
required
computation time
may increase.
Edition 12.2003