Configuring the fieldbus
6.2 Communication via RS485
Frequency inverters with Control Units CU230P-2 HVAC, CU230P-2 DP, CU230P-2 CAN
Operating Instructions, 01/2011, FW 4.4, A5E02430659B AD
131
The telegram runtime is longer than just purely adding all of the character runtimes
(=residual runtime). You must also take into consideration the character delay time between
the individual characters of the telegram.
: : :
: : :
67;
/*(
$'5
Q
%&&
67;
/*(
$'5
Q
%&&
&KDUDFWHUGHOD\WLPH
&KDUDFWHUUXQWLPH
0D[LPXPUHPDLQLQJWHOHJUDPUXQWLPH
Residual runtime
(compressed telegram)
50% of compressed
telegram residual runtime
Figure 6-10 Telegram runtime as the sum of the residual runtime and character delay times
The total telegram runtime is always less than 150% of the pure residual runtime.
Before each request telegram, the master must maintain the start delay. The start delay
must be > 2 × character runtime.
The slave only responds after the response delay has expired.
: : :
: : :
: : :
: : :
6WDUWGHOD\
6WDUWGHOD\
5HVSRQVHGHOD\
5HTXHVWIURPPDVWHU
5HTXHVWIURP
WKHPDVWHU
6ODYHUHVSRQVH
67; /*( $'5
Q
%&&
67; /*( $'5
%&&
67; /*(
%&&
Q
Figure 6-11 Start delay and response 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 6- 28 Duration of the start delay
Baud rate in bit/s
Transmission time per character (= 11 bits)
Min. start delay
9600
1.146 ms
> 2.291 ms
19200
0.573 ms
> 1.146 ms
38400
0.286 ms
> 0.573 ms
57600
0.191 ms
> 0.382 ms
115200
0.059 ms
> 0.117 ms
Note: The character delay time must be shorter than the start delay.
Summary of Contents for SINAMICS G120 CU230P-2
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