Overview Of The 3 Data Transfer Types, Fm 458 ←→ Simatic-Cpu - Siemens SIMADYN D FM 458 User Manual

Configuring
4.3.1 Overview of the 3 data transfer types, FM 458 ← ← ← ← → → → → SIMATIC-CPU
Designation Number of data
1. 4 bytes to
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
max. approx. 125
sets/blocks
data sets with each
max. 240 bytes
(refer below.)
Table 4-1 Data transfer, SIMATIC-CPU
All of the 3 data transfer types can be used in parallel.
4-6
Configuring Speed
FM 458: When PAS7 is
called, an interrupt
Block PAS7
is initiated on the
SIMATIC-CPU:
SIMATIC CPU,
OB40, etc.
e.g. OB40
(if a higher priority
interrupt isn't being
processed at
precisely that
time).
FM 458: When a block is
called, data is
blocks S7RD,
S7WR immediately read-
out of the memory
SIMATIC-CPU:
or written into the
transfer commands
memory.
for the I/O
(periphery)
FM 458: The data
"virtual associated with a
connections" telegram are read
with blocks or sent when the
block is called.
@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
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.
Application Module FM 458 - User Manual
6DD1904-0AE0 Edition 12.2001