Telegram; Structure Of The Fieldbus Telegram - Leuze electronic MA 248i Original Operating Instructions

10

Telegram

10.1

Structure of the fieldbus telegram

All operations are performed by control and status bits. Two bytes of control information
and two bytes of status information are available for this purpose. The control bits are a part
of the output module and the status bits are a part of the input bytes. The data starts with
the third byte.
If the actual data length is longer than the data length configured in the gateway, only part
of the data is transmitted; the remaining data is lost. In this case, the DL (data loss) bit is set.
The following telegram structure is used between PLC -> fieldbus gateway:
7
ND Address 4
This telegram structure is used between fieldbus gateway -> PLC:
7
ND
DLC7
Only the data part with the corresponding frame (e.g., STX, CR & LF) is then transmitted
between the fieldbus gateway and the Leuze end device. The two control bytes are
processed by the fieldbus gateway.
The corresponding control and status bits and their meaning are specified in section 10.2
and section 10.3.
Further information on the broadcast control bytes and address bits 0 ... 4 can be found in
chapter "Modular interfacing unit MA 3x (S4 switch position C)" on page 100.
Leuze electronic
6 5
Address 3 Address 2
Data byte / parameter byte 0
Data byte / parameter byte 1
6 5 4
BO DL BLR
DLC6 DLC5 DLC4
Data byte / parameter byte 0
Data byte / parameter byte 1
4 3 2
Address 1 Address 0
CTB SFB
...
3 2
DEX SMA
DLC3 DLC2
...
MA 248i
1 0
Broadcast Command
mode
R-ACK
1 0
W-ACK
DLC1 DLC0
Telegram
Control byte 0
Control byte 1
Data
Status byte 0
Status byte 1
Data
49