Mailbox 2.0 Transmission Method; Message; Figure 47: Communication Via Mailbox 2.0 - WAGO 750 Product Manual

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8.2 Mailbox 2.0 Transmission Method

The Mailbox 2.0 defines a service to transport data full duplex via a defined channel. The
service (see Diagnostic Service "IOL_DIAG") provides access to data areas (see Access
to Data Areas).
Example:
A sender wants to transfer 10 bytes (the character string "Hello WAGO") to a receiver via
a 4-byte wide channel.

8.2.1 Message

The Mailbox 2.0 process packs the data into messages. A message contains a header
and user data. There are two message types.
Message with simple header:
Message with extended header:
Structure of the Simple Header
Bit 7
0
Legend
0:
Length
Structure of the Extended Header
Bit 7
Legend
1 + 0:
Length High + Length Low:
Protocol ID
A message that uses this header can contain 16383 bytes of user data. In addition, the
message can have a protocol ID. This protocol ID allows the message to include a logical
meaning.
Product manual | Version: 1.1.0
Proportional Valve Module 2-3-4
Bit 6 Bit 5
Bit 6
1 0
Figure 47: Communication via Mailbox 2.0
Bit 4 Bit 3
Length
Simple header
Data element length max. 127 bytes
Bit 5 ... 0
Length High
Extended header
Data element length max. 16383 bytes
Protokoll_ID 0 ... 255
Appendix
Bit 2 Bit 1 Bit 0
Bit 7 ... 0 Bit 7 ... 0
Length Low Protocol ID
77