Elpro Technologies 105U-G Spécifications télécharger pdf (Page 60)

Application Note

Using ELPRO 805U Modems with Profibus

©ELPRO Technologies Pty Ltd August 2001

Page 2 of 7 APP_805U_PROFIBUS_R1-0.Doc

Siemens recommends connecting Profibus terminal “A” to the green wire in a cable, and

connecting Profibus terminal “B” to the red wire. To connect to an ELPRO modem to a

Siemens Profibus LAN wired in this way, connect the green wire to the terminal marked

“B” on the modem, and connect the red wire to the terminal marked “A” on the modem.

Bus Termination

The ELPRO modems have a switch to switch in a terminating resistor. The termination

impedance is approximately 330 Ω, which is considerably higher than the recommended

value for Profibus networks. Nevertheless, for short distances (< 100 m) this termination

will be suitable. For terminating longer segment lengths, a 270Ω resistor should be

installed across the “A” and “B” terminals of the modem, resulting in a termination

impedance of 150Ω (cable type “A” - 22AWG). Alternatively, install a 180 Ω resistor for

a termination impedance of 117 Ω (cable type “B” - 24 AWG).

Profibus Bus Parameters

The ELPRO 805U Radio Modem introduces an additional delay in data transmission.

This delay is approximately 8.5 mSec. The Profibus network must be configured for this

additional delay.

To account for this delay, the T_Slot parameter (Slot Time) must be adjusted in the

Profibus Configuration. The T_Slot parameter must be increased by the amounts in the

following table.

The Profibus Master must also increase the delay between successive transmissions to

ensure that messages received at the slave are received seperately, and are not lumped

together by the modem. This delay is adjusted by setting the Max_T_Sdr and T_Set value

in the profibus configuration.

Baud Rate T_Slot T_Set Max_T_Sdr

19,200 1500 200 450

93,750 4000 494 1023

These settings are demonstrated in the following sections for a Siemens S7 PLC.

1 2 ... 55 56 57 58 59 60 61 62 63 64 65 66

Pas de commentaire

Elpro Technologies 105U-G Spécifications Page 60