ABB TPU2000 User Manual

TPU2000/2000R Modbus/Modbus Plus/ Modbus TCP/IP Automation Guide
42
PREAMBLE
AA
OPENING FLAG
7E
(SYNCH FLAG)
BROADCAST
ADDR
FF
CRC-16
FRAME
CHECK
CLOSING
FLAG
MESSAGE
PREAMBLE
AA
OPENING FLAG
7E
(SYNCH FLAG)
BROADCAST
ADDR
FF
CRC-16
FRAME
CHECK
CLOSING
FLAG
MESSAGE
DEST
ADDRESS
SOURCE
ADDRESS
FUNCTION
CODE
COMMAND INCLUSION
( INCLUDES MODBUS)
MASTER
OUTPUT
PATH
ROUTER
COUNTER
TRANS
SEQUENCE
NUMBER
ROUTING
PATH
MODBUS
FRAME
MAC
Figure 5-7. Modbus Plus Message Frame Structure
Modbus Plus is a “token passing” network in that upon startup, a token is generated. The node with the token
acts as a host device. The node holds a token for a period of time and passes the token to the next node on the
network. The token rotation scheme is described in Figures 5-8 through 5-10.
PEER TO PEER EXAMPLE
Each node on the Network has a list
of all other node addresses on the
network. Upon Startup a token is
generated. The node in possession of
the token (Red Spot) may transmit.
When the node has finished
transmitting, it passes the token to
the next node. This node may, for
instance, may not wish to transmit.
The token will be passed to the next
node in the list before its time has
expired.
1
2
3
45
55 57 58 64
12345
55 57 58 64
56
List: 1,2,3,4,5,
55,57,58,64
List: 1,2,3,4,5,
55,56,58,64
56
Figure 5-8. Modbus Plus Token Rotation Explanation
If so the token is passed to the next
node, which sends a message...
… and so on in a fixed sequence
so that every node is guaranteed
network access within a
predetermined time slice.
1
2
3
45
55 57 6456
58
1
2
3
45
55 5756 58
64
List: 1,2,3,4,5,
55,56,57,64
List: 1,2,3,4,5,
55,56,57,58
Figure 5-9. Modbus Plus Token Rotation Explanation

ABB TPU2000 Specifications

General

Brand	ABB
Model	TPU2000
Category	Computer Hardware
Language	English