
70
SM-Applications Modules & Motion Processors User Guide
Issue Number: 4
If the parameter to be read does not exist, the End of transmission character (Ctrl & D)
is returned.
The checksum is derived by exclusive ORing the message bytes (characters) together
excluding the STX character and the checksum, i.e. Checksum = M1 ^ M2 ^ P1 ^ P2 ^
D1 ^ D2 ^ ..... Dn ^ ETX. The checksum is an unsigned 8bit value and if this value is less
than 32 then 32 is added to it.
6.1.1.2 Writing to a parameter
The following tables show the message constructs for writing to a parameter.
The following rules apply to the data field:
1. The maximum length is 12 characters.
2. The field may contain leading spaces, but not after any other character.
3. A sign character is optional. No sign indicates positive.
4. A decimal point is optional. This can appear at any point in the data field, but not
before the sign or before 10 numbers (i.e. the value written should not have more
than 9 decimal places). If the decimal point is not in the same position as used by
the parameter, some accuracy may be lost or extra decimal places added(e.g. if
D1
Data: 1
st
digit
D2
Data: 2
nd
digit
-
-
Dn
Data: n
th
digit
ETX
End of text (Ctrl & C)
Checksum
Table 6-2 Slave response (if request was correct and parameter exists)
Character
Description
Table 6-3 Master request
Character
Description
EOT
End of transmission (Ctrl & D)
A1
Second Processor address: 1
st
digit
A1
Second Processor address: 1
st
digit
A2
Second Processor address: 2
nd
digit
A2
Second Processor address: 2
nd
digit
STX
Start of text (Ctrl & B)
M1
Menu number: 1
st
digit
M2
Menu number: 2
nd
digit
P1
Parameter number: 1
st
digit
P2
Parameter number: 2
nd
digit
D1
Data: 1st digit
D2
Data: 2nd digit
-
-
Dn
Data: nth digit
ETX
End of text (Ctrl & C)
Checksum
Содержание Digitax ST Indexer
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