Description of the object dictionary

Overview

This chapter contains a description of all objects of the object dictionary (OD) of the Nanotec controllers.

You will find information here on:

  • Functions
  • Object descriptions ("Index")
  • Value descriptions ("Subindices")
  • Descriptions of bits
  • Description of the object

Structure of the object description

The description of the object entries always has the same structure and usually consists of the following sections:

Function
The function of the object dictionary is briefly described in this section.
Object description
This table provides detailed information on the data type, preset values and similar. An exact description can be found in section "Object description"
Value description
This table is only available with the "Array" or "Record" data type and provides exact information about the sub-entries. A more exact description of the entries can be found in section "Value description"
Description
Here, more exact information on the individual bits of an entry is provided or any compositions explained. A more exact description can be found in section "Description"

Object description

The object description consists of a table that contains the following entries:

Index
Designates the object index in hexadecimal notation.
Object name
The name of the object.
Object Code
The type of object. This can be one of the following entries:
  • VARIABLE: In this case, the object consists of only a variable that is indexed with subindex 0.
  • ARRAY: These objects always consists of a subindex 0 – which specifies the number of sub-entries – and the sub-entries themselves, beginning with index 1. The data type within an array never changes, i.e., sub-entry 1 and all subsequent entries are always of the same data type.
  • RECORD: These objects always consists of a subindex 0 – which specifies the number of sub-entries – and the sub-entries themselves, beginning with index 1. Unlike an ARRAY, the data type of the sub-entries can vary. This means that, e.g., sub-entry 1 may be of a different data type than sub-entry 2.
  • VISIBLE_STRING: The object describes a character string coded in ASCII. The length of the string is specified in subindex 0; the individual characters are stored beginning in subindex 1. These character strings are not terminated by a null character.
Data type
The size and interpretation of the object is specified here. The following notation is used for the "VARIABLE" object code:
  • A distinction is made between entries that are signed; these are designated with the prefix "SIGNED". For entries that are unsigned, the prefix "UNSIGNED" is used.
  • The size of the variable in bits is placed before the prefix and can be 8, 16 or 32.
Savable
Described here is whether this object is savable and, if so, in which category.

There are also the following table entries for the "VARIABLE" data type:

Access
The access restriction is entered here. The following restrictions are available:
  • "read/write": The object can both be read as well as written
  • "read only": The object can only be read from the object dictionary. It is not possible to set a value.
PDO mapping
Some bus systems, such as CANopen or EtherCAT, support PDO mapping. Described in this table entry is whether the object can be inserted into a mapping and, if so, into which. The following designations are available here:
  • "no": The object may not be entered in a mapping.
  • "TX-PDO": The object may be entered in an TX mapping.
  • "RX-PDO": The object may be entered in a RX mapping.

Value description

Listed in the table with the "Value description" heading are all data for sub-entries with subindex 1 or higher. The table contains the following entries:

Subindex
Number of the currently written sub-entry.
Name
Name of the sub-entry.
Data type
The size and interpretation of the sub-entry is specified here. The following notation always applies here:
  • A distinction is made between entries that are signed; these are designated with the prefix "SIGNED". For entries that are unsigned, the prefix "UNSIGNED" is used.
  • The size of the variable in bits is placed before the prefix and can be 8, 16 or 32.
Access
The access restriction for the sub-entry is entered here. The following restrictions are available:
  • "read/write": The object can both be read as well as written
  • "read only": The object can only be read from the object dictionary. It is not possible to set a value.
PDO mapping
Some bus systems, such as CANopen or EtherCAT, support PDO mapping. Described in this table entry is whether the sub-entry can be inserted into a mapping and, if so, into which. The following designations are available here:
  • "no": The object may not be entered in a mapping.
  • "TX-PDO": The object may be entered in an RX mapping.
  • "RX-PDO": The object may be entered in a TX mapping.

Description

This section may be present if use requires additional information. If individual bits of an object or sub-entry have different meaning, diagrams as shown in the following example are used.

The object has 8 bits (bit 0 and bit 1 with different functions). Bits 2 and 3 are grouped into one function; the same applies for bits 4 to 7.

Example [4]
Description of bit 4 up to and including bit 7; these bits are logically related. The 4 in square brackets specifies the number of related bits. A list with possible values and their description is often attached at this point.
Example [2]
Description of bits 3 and 2; these bits are logically related. The 2 in square brackets specifies the number of related bits.
  • Value 00b: The description here applies if bit 2 and bit 3 are "0".
  • Value 01b: The description here applies if bit 2 is "0" and bit 3 is "1".
  • Value 10b: The description here applies if bit 2 is "1" and bit 3 is "0".
  • Value 11b: The description here applies if bit 2 and bit 3 are "1".
B
Description of bit B; no length is specified for a single bit.
A
Description of bit A; bits with a gray background are not used.