Siemens SIMATIC S5 Manual page 192

S5-95U, SINEC L2
Calculating the Target Rotation Time
Assuming that you have defined the SET, ST, SDT 1 and SDT 2 arguments as listed in the table
entitled "Defining the Arguments of Basic Parameters for the S5-95U as a Function of the Baud
Rate" on page A-4, you can calculate the target rotation time required for the following types of
transmission:
• Standard connection
• PLC to PLC connection
• Cyclical I/O
Proceed as follows to calculate the target rotation time:
Determine the maximum possible number of frames for each different type of frame (for
example, SDN or SDA frames)
Out of these data and using the following table and the explanations to the token frame,
calculate the basic load. The values given in the table are specified in bit time units.
Add 11 bit time units to the basic load for every byte transmitted. The result is your worst-case
target rotation time.
Type of Frame
1
Token
2
SDN
3
SDA
4
SRD
1
Number of token frames = number of active stations on the SINEC L2 network
2
SDN (Send Data with No acknowledge) = data transmission without acknowledgement;for standard
connection (only broadcast)
3
SDA (Send Data with Acknowledge) = data transmission with acknowledgement; for standard connection
(not broadcast) and PLC to PLC connection
4
SRD (Send and Request Data) = data transmission and data request with comfirmation ; for Cyclic I/O
An example of calculating the target rotation time can be found on the next pag
EWA 4NEB 812 6112-02
9.6 19.2
70 70
170 190
180 185
270 270
DB1 Parameters, DB1 PAFE, TRT
Baud Rate in kbaud
93.75 187.5
70 75
210 230
190 230
270 280
500 1500
145 345
480 1120
425 1040
500 1160
A-5