PROFIBUS Manual
The field
SYN |
designates the 33 bit synchronization pause.
The synchronization pause marks the beginning of a new telegram sequence.
Example of a sequence:
A master receives the token from its colleague:
SYN |
SD4 |
DA |
SA |
It sends a telegram without a data field:
SYN |
SD1 |
DA |
SA |
FC |
FCS |
ED |
and receives a short confirmation in reply.
SC |
The master sends another telegram without a data field:
SYN |
SD1 |
DA |
SA |
FC |
FCS |
ED |
and receives a telegram with variable length in reply:
SD2 |
LE |
LEr |
SD2 |
DA |
SA |
FC |
PDU |
FCS |
ED |
The master sends a telegram with variable length
SYN |
SD2 |
LE |
LEr |
SD2 |
DA |
SA |
FC |
PDU |
FCS |
ED |
and receives no reply.
The master passes on control and sends a token telegram:
SYN |
SD4 |
DA |
SA |
