Siemens 6ES7 972-4AA02-0XA0 - Diagnostics Message Frame; Message Frame Structure; Contents of the Message Frame

User´s Guide Power Rail Booster Version 12/2005
Copyright © Siemens AG 2005 All rights reserved. 6ES7 972-4AA02-0XA0 Page 35 of 49
7.2 Diagnostics Message Frame
The PRB's SF contact can be evaluated in two different ways.
• DIP switch DIP-6Æ“Off“: The PRB's SF contact can be evaluated in two
different ways, as described in chapter
7.1
• DIP switch DIP-6Æ“On“: The system issues a bit-serial diagnostics message
frame via the SF contact to terminal 14. Evaluation
is carried out by means of a standard function block
for S7 as described in chapter
9.1.3
The system transfers the message frame on an event-driven basis. A new transfer
always takes place when the status of one or more bits in the message frame
changes, e.g. in the case of a coming and going error. If the status of one or more bits
changes while a message frame is being sent or in the break between two message
frames (approximately 1 second), it is transferred in the next status message frame. If
the status changes more than once in this time – such that the status bits of the first
message frame are valid again at the end of the message frame break – the system
does not send a new status message frame, since the current status corresponds to
that of the last message frame! If there is a change, the system carries out
transmission with the current status bits.
7.2.1 Message Frame Structure
The transferred character is one byte comprising eight bits of user data. For
synchronization, the system additionally transfers one start bit, one zero bit and one
stop bit. Data backup is carried out with one parity bit. The system functions with
even parity.
Fig. 29: Structure of the Diagnostics Message Frame
7.2.2 Contents of the Message Frame
The following table lists the data bits and explains their meanings.
Bit Name Meanin
g
Start bit Start Short circuit on Power Rail
0 Bit Zero bit Se
q
uence bit lo
g
ical 0
7
(
MSB
)
SF 0=OK 1=Grou
p
error
6 KS 0=OK 1=Short circuit on Power Rail
5 Limit Tem
p
0=OK 1=Limit tem
p
erature reached
4 Over Tem
p
0=OK 1=Overtem
p
erature reached
3 <Reserve> <Reserve>
2 <Reserve> <Reserve>
1 Bd-Lost 0=OK 1=Baud rate lost
0
(
LSB
)
<Reserve> <Reserve>
Parit
y
Parit
y
Parit
y
bit
(
even
)
Sto
p
bit Sto
p
Sto
p
bit lo
g
ical 1
Fig. 30: Contents of the Diagnostics Message Frame
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