HEIDENHAIN PWM 20 - Manual (Page 226)

November 2014 Interface description 227
 Quality improvement: Cyclic sampling every 25 µs with full "read and write" mode possible;
position values available in the subsequent electronics after only approx. 10 µs.
 Online diagnostics through valuation numbers that indicate the encoder’s current functional
reserves and make it easier to plan machine use
 Safety system: EnDat 2.2 was conceived for safety-related machine designs.
Two independent position values for error detection. Two independent error messages.
Checksums and acknowledgments. Forced dynamic sampling of error messages and CRC
formation by subsequent electronics.
Benefits of purely serial transmission specifically for EnDat 2.2 encoders
 Cost optimization through simple subsequent electronics with EnDat receiver component
and simple connection technology: Standard connecting element (M12; 8-pin), single-
shielded standard cables and less complex wiring.
 Minimized transmission timesthrough high clock frequencies up to 16 MHz. position
values are available in the subsequent electronics after approx. 10 µs.
 Support for state-of-the-art machine designs, e.g. direct drive technology
Versions The extended EnDat interface version 2.2 is compatible in its communication, command set and
time conditions with version 2.1, but also offers significant advantages. It makes it possible, for
example, to transfer additional information with the position value without sending a separate
request for it. For this purpose the interface protocol was expanded and the time conditions
(clock frequency, calculating time, recovery time) were optimized.
Ordering
designation The order designations define the central specifications and give information about:
 Typical power supply range
 Command set
 Availability of incremental signals
 Maximum clock frequency
The second character of the order designation identifies the interface generation. For encoders
of the current generation the order designation can be read out from the encoder memory.
Command set
The command set is the sum of all available MODE commands (see "Selection of transmission
type"). The EnDat 2.2 command set includes the EnDat 2.1 MODE commands. When a MODE
command from the EnDat 2.2 command set is transmitted to EnDat-01 subsequent electronics,
the encoder or the subsequent electronics may generate an error message.
Incremental signals
EnDat 2.1 and EnDat 2.2 are both available with or without incremental signals. EnDat 2.2
encoders feature a high internal resolution. Therefore, depending on the control technology
being used, interrogation of the incremental signals is not necessary. To increase the resolution
of EnDat 2.1 units, the incremental signals are interpolated and evaluated in the subsequent
electronics.
Power supply
Encoders with ordering designations EnDat 02 and EnDat 22 have an extended power supply
range.
Functions The EnDat interface transmits absolute position values or additional physical quantities (only
EnDat 2.2) in an unambiguous time sequence and serves to read from and write to the encoder’s
internal memory. Some functions are available only with EnDat 2.2 MODE commands.
Position values can be transmitted with or without additional information. The additional
information types are selectable via the Memory Range Select (MRS) code. Other functions
such as parameter reading and writing can also be called after the memory area and address
have been selected. Through simultaneous transmission with the position value, additional data
can also be requested of axes in the feedback loop, and functions executed with them.
Parameter reading and writing is possible both as a separate function and in connection with
the position value. Parameters can be read or written after the memory area and address are
selected.