Siemens AS 488/TM manual Connection of PROFIBUS-PA using DP/PA coupler, Driver block Description

This catalog is out of date, see note on page 3

Process I/Os

PROFIBUS-PA

Connecting PROFIBUS-PA to AS 488/TM

■Design

Connection of PROFIBUS-PA using DP/PA coupler

The PROFIBUS-DP is connected to the AS 488/TM via an IF 964-DP interface module which can be plugged into an EXM 478 extension module.

DP/PA couplers are available in two versions: an Ex version with max. 100 mA output current and a non-Ex version with 400 mA output current. The DP/PA couplers are mounted together with a load power supply for DC 24 V on an S7-300 rail outside the haz- ardous area. A 9-pin Sub-D plug is used for connection to the

PROFIBUS-DP.

Four screw terminals are available for the PROFIBUS-PA con- nection with the non-Ex version. The PROFIBUS-PA cable can be looped through if required, or terminated by a selectable re- sistor. With the intrinsically-safe Ex version, the DP/PA coupler is always at the end of the cable, and the terminating resistor is ac- tivated. Only two screw terminals are available for the PROFIBUS-PA connection.

Each PA field device occupies a PROFIBUS address on the DP line.

Connection of PROFIBUS-PA using DP/PA link

The PROFIBUS-DP is connected to the AS 488/TM via an IF 964- DP interface module which can be plugged into an EXM 478 ex- tension module.

■Mode of operation

Users have access to the field devices on the PROFIBUS-PA using downloadable PA driver blocks which are combined in a driver library. These driver blocks support the cyclic services of the PA profile, and permit productive operation of a large num- ber of PA field devices from various vendors (e.g. Siemens, Endress+Hauser, Bürkert, Krohne, VEGA, NELES, etc.) which comply with this PA profile.

Limitation:

When linking PA field devices via the DP/PA link, the DP device must accept parameterization telegrams with a length of

10 byte.

Driver block	Description
PAAI	Analog input block for
	PROFIBUS-PA
	(representative of transmitter)
PAAO	Analog output block for
	PROFIBUS-PA
	(representative of actuators such
	as drives, controllers etc.)
PADI	Discrete value input block for
	PROFIBUS-PA
PADO	Discrete value block for
	PROFIBUS-PA
	(representative of actuators such
	as valves etc.)

The DP/PA link comprises the IM 157 interface module and up to

5DP/PA couplers which are connected together via S7-300 standard bus plugs. By combination of the IM 157 with Ex or non-Ex versions of the DP/PA coupler, DP/PA link versions can be generated for use in hazardous and non-hazardous areas. The DP/PA link is mounted together with a load power supply for DC 24 V on an S7-300 rail outside the hazardous area. A 9-pin Sub-D plug on the IM 157 interface module is used for connec- tion to the PROFIBUS-DP.

Four screw terminals are available on the DP/AP couplers of the non-Ex version for the PROFIBUS-PA connection. The PROFIBUS-PA cable can be looped through if required, or ter- minated by a selectable resistor. With the intrinsically-safe

Ex version, the DP/PA coupler is always at the end of the cable, and the terminating resistor is activated. Only two screw termi- nals are available for the PROFIBUS-PA connection.

Only the DP/PA links occupy a PROFIBUS address on the

DP line. Each DP/PA link provides a separate address range for each of the subordinate PA field devices.

The communications interface permits operation of the PROFIBUS-PA on the AS 488/TM, and thus also the coexistence of additional masters of class 2 on the PROFIBUS-DP, setting of

45.45kbit/s as the transmission rate, as well as higher transmis- sion rates up to 12 Mbit/s.

8/18 Siemens PLT 112 · 2002