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Appendix
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Product manual | Version: 2.0.0
8DIO FLD EC DC 24V 2.0A
Figure 40: Structure of the Ethernet Frame for AoE
The upper part shows the structure of an EtherCAT frame with mailbox area. The size of
the mailbox area is limited to a maximum of 1472 bytes. The actual length of the mailbox
is entered in the “Length” field.
The lower part shows only the mailbox area as an excerpt from the EtherCAT frame. It
contains the protocol data structure of the integrated protocol. With AoE, this contains the
protocol data structure of the ADS protocol:
• AoE uses mailbox header type 1 and includes 6 bytes.
• The AoE header contains 32 bytes.
• A maximum of 1434 bytes (= 1472 bytes − 6 bytes − 32 bytes) are thus available for
the AoE data area (AoE data).
14.1.3 Overview of the Structure of the AoE Frame
The basic structure of the AoE frame is described in the following table:
Table 84: Structure of the AoE Frame
Offset
Name
Type
Description
0 ... 1
Length
Word
Length of the mailbox data
2 … 3
Address
Word
If the EtherCAT master is the client: station
address of the source.
If the EtherCAT slave is the client: station
address of the target.
4
Channel
Unsigned6
Value 0 (fixed)
Priority
Unsigned2
Value 0 (fixed)
5
Type
Unsigned4
Value 1 (fixed)
Label for an AoE mailbox frame
Cnt
Unsigned3
Counter for mailbox services (value range:
1 ... 7; is reset to 1 after 7; 0 is reserved)
Reserved
Unsigned1
Value 0 (fixed)
6 ... 37
AoE Header
Unsigned8[32]
AoE header; see the following table “Struc-
ture of the AoE Header.”
38 ... 38 +
(n−1)
AoE Data
Unsigned8[n]
AoE Data Area
The AoE header (offset 6 to 37) contains the addresses of the transmitter and receiver,
plus the error code, the command ID and other information.
The AoE data area (from offset 38) contains the parameters of the individual ADS com-
mands. The structure of the data field depends on the specific ADS command. Some
commands do not require additional data. In this case, the AoE data area is omitted.
The structure of the AoE header within the AoEMailbox frame is described in the follow-
ing table.
