VIPA CP 240 RS232, Manual

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Chapter 6 CP 240 - M-Bus Manual VIPA System 200V
6-8 HB97E - CP - Rev. 11/30
Overview of M-Bus telegrams
M-Bus differentiates the following 4 telegrams:
•
Single character
The single character serves the acknowledgment of correctly received
telegrams (syntax and check sum)
•
Short frame
For a short frame telegram you always have to define 3 bytes. The M-
Bus takes them as telegrams of the CP 240 to a slave, e.g.:
- SND_NKE: initialize counter
- REQ_UD2: request counter data
•
Control frame
The control frame requires 4 defined bytes. Herewith you may send M-
Bus control commands like e.g.:
- set baud rate of the slave
- execute slave reset
•
Long frame
The long frame contains the user data and has consequently a variable
length. Here the user data may be sent in both directions, e.g.:
- send user data to the slave
- select slave via secondary address
- set date and time of a slave
- select data area to read from
Please regard that every M-Bus telegram has to be prefixed by one byte
that specifies the baud rate to use. At error-free reception, the Byte 0 of the
receive DB contains 00h. A value <> 00h indicates an error.
At the transfer of a M-Bus telegram to the CP 240, the telegram type is
automatically detected; the data is automatically included into the
according telegram structure and put out via M-Bus. With the call of the
VIPA handling blocks exclusively the following data (marked green) must
be transferred, depending on the telegram. Here the sum of these bytes
has to be set as length value.
Single charact. Short frame Control frame Long frame
Baud rate Baud rate Baud rate Baud rate
E5h 10h Start 68h Start 68h Start
C field L field = 3 L field
A field L field = 3 L field
Check sum 68h Start 68h Start
Stop 16h C field C field
A field A field
CI field CI field
Check sum
Stop 16h
User Data
(0...252Byte)
Check sum
Stop 16h
Length for
handling block: 2 Length for
handling block: 3 Length for
handling block: 4 Length for
handling block:
5...n
Overview