Chronological Sequence Of Communication - JUMO IPC 300 Operating Manual

2 Protocol description
Broadcast
Instruction from the master to all slaves via device address 0. The connected slaves do not respond.
This makes it possible to transfer a specific setpoint value to all slaves, for example. In such a case, the
correct acceptance of the value by the slaves should be checked by a subsequent readout of the setpoint
value.
A data request with device address 0 does not make sense.
2.4

Chronological sequence of communication

Time diagram
Example of the chronological sequence for communication based on 1 Modbus master (e.g., SCADA
software on a PC or a PLC) and 2 IPC 300s as Modbus slave 1 and Modbus slave 2:
Master
UART:
Slave1
UART:
Slave2
UART:
t1
Identifies the end of the request:
According to the Modbus specification it is at least 3.5 times as long as the transfer time for 1 character,
depending on the baud rate. In the IPC 300 the time is:
• at 9600 baud: 4.1 ms
• at 19200 baud: 2.1 ms
• at 38400 baud: 1.1 ms
t2
Internal processing time:
The time required by the power controller to process the request it has received and prepare the re-
sponse. In the IPC 300 it is typically 1 to 3 ms and a maximum of 6 ms.
t3
Identifies the end of the response:
Same duration as t1.
Chronological sequence
The master sends a data request for slave 1. After the last character is sent, all connected IPC 300
slaves wait for a time of t1. Then the instruction is evaluated.
Slave 2 discards the instruction because the device address does not match. On the other hand, slave
10
Data request
(for Slave 1)
Receive
blocked
Receive
t
1
Receive
Response
Send
Receive
t
2
Data request
Send
Receive
Receive
t
3
t