Parameter Display and Configuration via
CICT
CAN-CBM-DP
Software Manual Rev. 2.0
76
Further Explanations about Parameters
Parameter
Format
: Converting the Data Format
Parameter
Format
is used to convert the data format.
Background: Messages which are longer than 1 byte are normally transmitted in Intel notation (lowbyte
first) in the CAN network, while the Siemens PLC operates in Motorola format (highbyte first). These
formats can be converted via the format byte.
Starting with bit 7 of the format byte you can decide whether the following byte is to be converted as
well, i.e. swapped, or not. If a ‘1’ is specified for a byte, the following bytes are converted until the next
‘0’ transmitted. The functionality can be explained best by means of an example.
Example:
A CAN telegram has got a date in Intel format in the first byte, followed by 2 bytes which are
not to be swapped and a long word in the last 4 bytes which is in Intel format again.
Binary the following representation results for the format byte:
Bit No.
7
6
5
4
3
2
1
0
Bit of
Format
1
0
0
0
1
1
1
0
hexadecimal
8
E
action
begin
swap
end swap
un-
changed
un-
changed
begin
swap
swap
swap
end
swap
Data bytes
1
2
3
4
5
6
7
8
CAN frame
2 bytes
Intel format
byte 3
byte 4
4 bytes
Intel format
PLC data
2 bytes
Motorola format
byte 3
byte 4
4 bytes
Motorola format
From this the format byte results in 8E hex. If all eight bytes are to be swapped, for instance, value FE
hex is specified for the format byte.
The lowest bit is generally without significance, because the telegram and therefore the formatting have
been completed. The bit should always be set to 0.
If parameter
Format
has not been set, the default setting will be used. In default setting all bits are set
to ‘0’, i.e. no data is being converted.
