Watson-Marlow MM440 - Manual (Page 149)

Issue 10/06 3 Functions
MICROMASTER 440 Operating Instructions
6SE6400-5AW00-0BP0 149
The telegram has the following structure:
¾
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).
¾ 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).
¾ The same applies to double-word data: the high word is sent first followed by
the low word.
¾ 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.
¾ 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".
n net characters
STX LGE ADR 1. 2. n BCC
Fig. 3-39 Telegram structure
Information is coded as follows:
Abbreviation Significance Size Explanation
STX Start of text ASCII characters 02 hex
LGE Telegram length 1 byte Contains the telegram length
ADR Address 1 byte Contains the slave address and the
telegram type (binary coded)
--- Net characters Each one byte Net data, contents are dependent on
the request
BCC Block check character 1 byte Data security characters