How Page Addressing Works - Siemens SIMATIC S5 Manual

IM 308-C – addressing, diagnostics and use of the FB IM308C
Example: page
addressing
Table 9-3 How page addressing works
Activity
1. Write the number of the page
to the read/written into the
"page selection address"
byte.
L KF +18
T PY 255
2. You can now read or write
the actual address, for
example load I/O byte PY
193:
L PY 193
T MB 100
P-page addressing
Q-page addressing
9-8
The table below shows how page addressing works. Note that the mode
shown here by way of example illustrates P-page addressing.
In the example, the I/O byte PY 193 is read from the page having the page
number 18. Page 18 is on the second IM 308-C, the number of which is 16.
Memory areas in the IM 308-Cs
PY 254
...
...
PY 193
2
PY 192
1
Page 0
1st IM 308-C
(number of
Page 16
IM 308-C = 0)
PY 254
...
PY 193
PY 192
Page 16
In P-page addressing, part of the P area is replicated. The part in question is
from PY 192 to PY 254.
You can use PY 0 to PY 191 to address the central I/O modules in the
programmable controller.
In Q-page addressing, the Q area is replicated. The Q area extends from QB 0
to QB 254.
The page selection address is
loaded into the IM 308-C via the
I/O bus.
The IM 308-C sets a pointer to
15
page 18 and makes this page
...
15
available for read/write.
31
...
...
18
255
17
...
...
Page 240
16th IM 308-C
(number of the
IM 308-C = 240)
You have direct access to a
memory area of the IM 308-C.
15
31
...
18
17
Result
ET 200 Distributed I/O System
EWA 4NEB 780 6000-02a