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
Pepperl+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
27
Figure 5.3 Message exchange with flow control
5.5.1 Data transmission slave --> master
The transmission state machine is shown to understand how a single block is
transmitted and received. This protocol guarantees a basic flow control mechanism
from slave to master.
Figure 5.4 State machine for block tx slave --> master with PROFIBUS DP
MASTER Profibus DP
tx_buffer_full (bit 0)
handshake (byte 0)
rx_buffer_empty (bit 1)
rx_buffer_full (bit 1)
tx_buffer_empty (bit 0)
SLAVE
IN
OUT
tx buffer (byte 1 ... N
IN
)
handshake (byte 0)
rx buffer (byte 1 ...
N
OUT
)
0
1
2
N
IN
0
1
2
N
OUT
0
1
2
N
IN
0
1
2
N
OUT
rx data
tx data
First bit shown in transition --> IN[0].0 / TX Buffer Full = data written by slave
Second bit shown in transition --> OUT[0].0 /TX Buffer Empty = data read by master
master read tx buff
slave write tx buff
slave write tx buff
master read tx buff
A
0,0
D
0,1
B
1,0
C
1,1