Siemens ISI EN 50295 Brochure page 88

AS-Interface Slaves
I/O modules for operation in IP20 control cabinet
Module F90
■
Function
Principle of operation of the 16E module (3RG9 002-0DE00
and 3RG9 004-0DE00)
The 16 inputs are arranged in four groups of four inputs.
Only one group is permitted to be activated at a time. The PLC
activates each group in sequence and reads the four input sig-
nals into the process image of the inputs in each case. The user
program assigns the input information to the appropriate
groups, i .e. the output process image of the PLC must corre-
spond to the set output of the module otherwise input information
will be read in from the wrong group.
When a fault occurs in AS-i transmission, it can take up to three
AS-i cycles (15 ms) until the output image of the slave corre-
sponds to the output image of the master and therefore of the
PLC. It can also take three cycles to transfer the input image of
the slave. If messages to a particular slave are faulty over more
than three consecutive AS-i cycles, the slave outputs a "Config
error" to the master. The input image in the master is set to zeroes
and the fault bit is set in the PLC.
Example: Response of the output image and the input image
in the master and in the slave to faulty AS-Interface transfer
6
The example shows that the output image and input image are
not consistent in the master and slave until six AS-Interface
cycles have elapsed. The PLC cycle is not synchronous with the
AS-Interface cycle. For this reason, the time that must elapse be-
fore the output image and input image of the master and PLC are
consistent is extended by one AS-Interface cycle and one PLC
cycle respectively.
Formula for the cycle time:
4 · ((6 · 5 ms) + 5 ms + 10 ms) =180 ms
6/88 Siemens IK PI · 2004
Note 1:
The following function blocks (FBs) are available for
sequence control:
• FB 21 (E16-2433) for the AS-Interface master CP2433
(S5-95 U)
• FB 22 (E16-2430) for the AS-Interface master CP2430
(S5-115 U)
• FC 22 for S7
At least 30 ms must elapse between two function block calls for
a module to ensure that the switching status of the inputs can be
reliably read.
Note 2:
Programming examples can be requested from out
Technical Support, Tel. (+49 91 31) 74 38 33, or down-
loaded from the Internet:
Additional information is available from in the Internet under:
http://www.siemens.de/as-interface