For safety-related applications HEIDENHAIN offers rotary encoders, angle encoders and linear encoders with EnDat 2.2 interface. These encoders operate as single-encoder systems with purely serial data transmission via EnDat 2.2. Reliable transmission of the position is based on two independently generated absolute position values and on error bits, which are then provided to the safe control. In order to be able to use these encoders in safety-related applications, a control is required for the appropriate evaluation and processing of the encoder data.
Basically, two different implementation solutions for EnDat 2.2 are possible:
- EnDat Master Safe (EnDat master with monitoring functions)
The EnDat-Master Safe takes over parts of the safety functions, prepares encoder data and makes them available to the control. Preprocessing the data relieves the burden on the control. In this constellation, the EnDat master is integrated into the security chain. For this solution, HEIDENHAIN offers a tested safe EnDat master for use in FPGAs/ASICs.
- EnDat Master Basic
In this version, the EnDat master can be considered a black channel. It passes the encoder data unchanged to the control and is not integrated into the safety chain. The transfer of all safety functions to the subsequent control results in higher demands on the performance of the safety module. For example, safety-related data must be processed in the control cycle because, in contrast to an EnDat Master Safe, they are not buffered.
Depending on the safety strategy or the control architecture, the solution can be better suited with an EnDat Master Safe or with an EnDat Master Basic. This has to be decided on the basis of the application.
The requirements for implementation are described in detail in a separately available documentation from HEIDENHAIN. This includes, for example, the monitoring functions, specifications on the evaluation and processing of position values and error bits, and information about the electrical connection. Please request this documentation if necessary.