Position values -PROFIBUS-DP serial interface

PROFIBUS-DP;  The PROFIBUS is a non-proprietary, open  fieldbus according to the international  standard EN 50 170. The connecting of sensors through fieldbus systems minimizes the cost of cabling and reduces the number of lines between encoder and subsequent electronics.

Topology and bus assignment: The PROFIBUS-DP is designed as a linear structure. It permits transfer rates up to 12 Mbit/s. Both mono-master and multimaster systems are possible. Each master can serve only its own slaves (polling). The slaves are polled cyclically by the master. Slaves are, for example, sensors such as absolute rotary encoders, linear encoders, or also control devices such as motor frequency inverters.

Physical characteristics: The electrical features of the PROFIBUS-DP comply with the RS-485 standard. The bus connection is a shielded, twisted two-wire cable with active bus terminations at each end.

Initial confiuration:The characteristics of HEIDENHAIN encoders required for system configuration are included as “electronic data sheets”— also called device identification records (GSD)—in the gateway. These device identify cation records (GSD) completely and clearly describe the characteristics of a unit in an exactly defined format. This makes itpossible to integrate the encoders into the bus system in a simple and application friendlyway.

Confi guration:PROFIBUS-DP devices can be configured  and the parameters assigned to fit  the requirements of the user. Once these settings are made in the configuration tool with the aid of the GSD fi le, they are saved in the master. It then configures the PROFIBUS devices every time the network starts up. This simplifies exchanging of the devices: There is no need to edit or reenter the configuration data. Two different GSD fi les are available for selection: • GSD fi le for the DP-V0 profile • GSD fi le for the DP-V1 andDP-V2 profi les

PROFIBUS-DP profile : The PNO (PROFIBUS user organization) has defined standard, nonproprietary profiles for the connection of absolute encoders to the PROFIBUS-DP. This ensures high flexibility and simple configuration on all systems that use these standardized profiles.

DP-V0 profile: This profile can be obtained from the Profibus user organization (PNO) in Karlsruhe, Germany, under the order number 3.062. There are two classes defined in the profile, where class 1 provides minimum support, and class 2 allows additional, in part optional functions.

DP-V1 and DP-V2 profile: This profile can be obtained from the Profibus user organization (PNO) in Karlsruhe, Germany, under the order

number 3.162. This profile also distinguishes between two device classes: • Class 3 with the basic functions and • Class 4 with the full range of scaling and preset functions. Optional functions are defined in addition to the mandatory functions of classes 3 and 4.

Supported functions: Particularly important in decentralized field bus systems are the diagnostic functions (e.g. warnings and alarms), and the electronic ID label with information on the type of encoder, resolution, and measuring range. But programming functions such as counting direction reversal, preset/zero shift and changing the resolution (scaling) are also possible. The operating time and the velocity of the encoder can also be recorded.

Encoders with PROFIBUS-DP : Absolute encoders with integrated PROFIBUS-DP interface are connected directly to the PROFIBUS. LEDs on the

rear of the encoder display the voltage supply and bus status operating states. The coding switches for the addressing (0 to 99) and for selecting the terminating resistor are easily accessible under the bus housing. The terminating resistor is to be activated if the rotary encoder is the last participant on the PROFIBUS-DP and the external terminating resistor is not used.