PROFIBUS Manual

Time ratios

Time ratios

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Time ratios

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On any PROFIBUS, certain time ratios must be respected to ensure that a telegram sequence can function correctly.

 

After a synchronization pause lasting TSYN to mark the beginning of a sequence, the Request telegram is sent by the master to the slave. The slave should start its response no sooner than min TSDR (SDR = Station Delay of Responder), but no later than max TSDR. The min TSDR time must include at least the TQUI time of the in-line amplifier and repeater and the TRDY time of the master. In modern PROFIBUS-DP systems, min TSDR = 11. Slower PROFIBUS-FMS slaves have min TSDR values of up to 255 tBit. The master waits for a response from a slave for a maximum period of TSL (SL = slot). This time is determined by max TSDR.

Time ratios

Time ratios

 

All times listed here can be read and adjusted as FDL parameters.

 

 

Parameter

Bit rate in kBit/s

187.5

500

1500

3000

6000

12 000

TQUI

0

0

0

3

6

9

TSET

1

1

1

4

8

16

TRDY

11

11

11

11

11

11

min TSDR

11

11

11

11

11

11

max TSDR

60

100

150

250

450

800

TSL

100

200

300

400

600

1'000

Table of default values for times