HEIDENHAIN PWM 20 - Manual (Page 225)

226 HEIDENHAIN ATS Software User's Manual
Clock frequency /
cable length The clock frequency is variable—depending on the cable length (max. 150 m)—between
100 kHz and 2 MHz. With propagation-delay compensation in the subsequent electronics, either
clock frequencies up to 16 MHz are possible or cable lengths up to 100 m. For EnDat encoders
with order designation EnDat x2 the maximum clock frequency is stored in the encoder memory.
For all other encoders the maximum clock frequency is 2 MHz. Propagation-delay compensation
is provided only for order designations EnDat 21 and EnDat 22; for EnDat 02, see the notes
below.
Transmission frequencies up to 16 MHz in combination with large cable lengths place high
technological demands on the cable. Due to the data transfer technology, the adapter cable
connected directly to the encoder must not be longer than 20 m. Greater cable lengths can be
realized with an adapter cable no longer than 6 m and an extension cable. As a rule, the entire
transmission path must be designed for the respective clock frequency.
Benefits of the
EnDat interface  Automatic configuration All information required by the subsequent electronics is already
stored in the encoder.
 High system security through alarms and messages for monitoring and diagnosis
 High transmission reliability through cyclic redundancy checks
 Datum shift for faster commissioning
Other benefits of EnDat 2.2
 Uniform interface for all absolute and incremental encoders
 Additional information (limit switches, temperature, acceleration)
EnDat 01
EnDat Tx
EnDat Hx 2 MHz (see “without propagation-delay compensation” in the diagram)
EnDat 21 2 MHz
EnDat 02 2 MHz or
8 MHz or 16 MHz (see notes)
EnDat 22 8 MHz or 16 MHz
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Note
Notes on EnDat 02:EnDat 02 encoders typically have a pluggable cable assembly
(e.g. LC 415). In choosing the version of the adapter cable, the customer also dec
ides whether the encoder will be operated with incremental signals or without them.
This also affects the maximum possible clock frequency. For adapter cables with
incremental signals the clock frequency is limited to at most 2 MHz; see EnDat 01.
For adapter cables without incremental signals the clock frequency can be up to 16 MHz.
The exact values are stored in the encoder’s memory.