Siemens MICROMASTER 440 Operating Instructions Manual page 149

Issue 10/06
The telegram has the following structure:
Each telegram begins with the start character STX (= 02 hex), followed by the
length information (LGE) and the address byte (ADR). The net characters then
follow. The telegram is terminated by the BCC (Block Check Character).
For single-word data (16 bit) in the net data block (= net character block), the
high byte (first character) is always sent and then the low byte (second
character).
The same applies to double-word data: the high word is sent first followed by
the low word.
The necessary settings / parameter assignments must be made both at the
master as well as at the slave and can no longer be changed in bus operation.
The protocol does not identify tasks in the net characters. The contents of the
net characters/data for the MICROMASTER drives is discussed in Section
3.7.1.2 "Structure of the net data".
Fig. 3-39
Information is coded as follows:
Abbreviation Significance
STX
LGE
ADR
---
BCC
MICROMASTER 440 Operating Instructions
6SE6400-5AW00-0BP0
STX LGE ADR
Telegram structure
Start of text
Telegram length
Address
Net characters
Block check character 1 byte
1. 2.
n net characters
Size Explanation
ASCII characters 02 hex
1 byte Contains the telegram length
1 byte Contains the slave address and the
telegram type (binary coded)
Each one byte Net data, contents are dependent on
the request
Data security characters
3 Functions
n BCC
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