Instruction manual

Connection box C-BOX 300
The C-BOX PROFIBUS protocol implementation
S
ubject to reasonable modifications due to technical advances. Copyright Pepperl+Fuchs, Printed in Germany
P
epperl+Fuchs Group • Tel.: Germany (06 21) 7 76-0 • USA (330) 4 25 35 55 • Singapore 7 79 90 91 • Internet http://www.pepperl-fuchs.com
Date od issue 07/25/2003
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5.5.2 Data transmission master --> slave
The receive state machine is shown to understand how a single block is transmitted
by the master and received by a slave.
This protocol guarantees a basic flow control mechanism from master to slave.
Figure 5.5 State machine for block rx ( slave <-- master ) with PROFIBUS DP
5.5.3 Resynchronization protocol
Resynchronization may be used at the master startup, both to detect if a slave is on
line or not, or to restart the messaging protocol from a predefined state. It is also used
during normal operations in case of errors requiring a protocol reset procedure to be
started.
Figure 5.6 State machine for syncronization action
First bit shown in transition --> OUT[0].1 / RX Buffer Full = data written by master
Second bit shown in transition --> IN[0].1 /RX Buffer Empty = data read by slave
slave read rx buff
master write rx buff
master write rx buff
slave read rx buff
A
0,0
D
0,1
B
1,0
C
1,1
Bits order:
-OUT [0].bit2 = Sync request -IN[0].bit2 = Sync acknowledge
error
Sync finish ack
0,0
Sync request
1,X
Sync request finish
0,1
Sync acknowledge
1,1
IN[0], IN[1], OUT[0], OUT[1]
reset
STARTUP
SYNCRONIZED
UNSYNCRONIZED
0
E
A B
D C