Communication
9.5 Communication using USS
Function Manual
Function Manual, 01/2011, 6SL3097-4AB10-0BP3
643
Start delay
The duration of the start delay must at least be as long as the time for two characters and
depends on the baud rate.
Table 9- 44 Duration of the start delay
Baud rate in
bits/s
Transmission time per character
(= 11 bits)
Transmission time
per bit
Min. start delay
9600 1.146 ms 104.170 µs > 2.291 ms
19200 0.573 ms 52.084 µs > 1.146 ms
38400 0.286 ms 26.042 µs > 0.573 ms
57600 0.191 ms 17.361 µs > 0.382 ms
115200 0.059 ms 5.340 µs > 0.117 ms
Note: The time between two characters must be shorter than the start delay.
STX
The STX block is a single-byte ASCII STX character (0x02) and indicates the beginning of
the message.
LGE
LGE is a single-byte block and specifies the number of bytes that follow in the telegram. It is
defined as the sum of
● User data characters (quantity n)
● Address byte (ADR)
● Block check character (BCC)
The actual overall telegram is, of course, two bytes longer because STX and LGE are not
counted in LGE.
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