Figure 3-8 Changing The Sign Of Life - Siemens Add 7 AddFEM Manual

AddFEM
or 0x03) and Code 2 (hexadecimal value: 0x0A or 0x0C).
Code 2 = 0x0A
Code 1 = 0x05

Figure 3-8 Changing the sign of life

For the AddFEM an Host is considered functional, if Code 1 and Code 2 are trans-
ferred alternatively as a SoL within a typical period of t
a state, an error has occurred and the system changes directly to the redundant
interface!
The sign of life with the code 0x05/0x0A is evaluated higher by definition by the
AddFEM than the SoL with the code 0x03/ 0x0C. The changeover controller for the
output data follows the higher–value sign of life. The system always transfers
those messages which contain the "higher–value" SoL code. If the current master
CPU or the master transmission link fails, the AddFEM also accepts the message
which contains the code 0x03/0x0C.
The master changeover can be initiated actively by the AP by changing the two
sign–of–life codes between AP A and AP B. If equivalent signs of life (occurring
only temporarily) occur, the old state is retained.
The AddFEM is changed over in accordance with the following algorithm:
Table 3-2
Bus interface A
supplies...
SoL 0x05/0x0A
SoL 0x05/0x0A
SoL 0x05/0x0A
SoL 0x03/0x0C
SoL 0x03/0x0C
SoL 0x03/0x0C
– None –
– None –
– None –
Exceeding of a specified monitoring time is decisive for the changeover.
The monitoring time is not a fixed setting and does not have to be configured on
the AddFEM. It is "learned" automatically by the AddFEM as described below.
AddFEM
C79000–G8076–C900–03
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t
cyc
Changeover of the AddFEM
Bus interface B
supplies...
SoL 0x03/0x0C
SoL 0x05/0x0A
– None –
SoL 0x03/0x0C
SoL 0x05/0x0A
– None –
SoL 0x03/0x0C
SoL 0x05/0x0A
– None –
t
! If a sign of life freezes in
cyc
Reaction of the AddFEM
Use data from bus interface A!
Retain old state because duplicate master!
Use data from bus interface A!
Retain old state because duplicate master!
Use data from bus interface B!
Use data from bus interface A!
Use data from bus interface B!
Use data from bus interface B!
Double fault! Set outputs to a safety–orien-
ted state, meaning zero signals!
Mode of Operation
3-15