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Message Structure
(request and answer have the same format)
The master system (PC) starts every session sending
the following message to the slave units connected :
<STX> + <ADR> + <WINDOW> + <COMMAND> +
<DATA> + <ETX> + <CRC>
where :
<STX>= 0x02
<ADR>= 0x80 + device number (0...31)
0xFF: brodcasting command
(recognized by all the devices, it
doesn't implicate any answer)
<WINDOWS>=' 000 '...' 999' window number
the meaning of the window
depends to the device type
<COMMAND>= 0x30 :window value reading
0x31 :window writing
<DATA> =
alphanumeric ASCII string
containing, in the case of writing
operation,the parameter to input
into the window addressed by
the field <WINDOW>This field
may have variable length
according to the data type
contained in the window where
you are working in. In the case of
reading request of a window, the
data field doesn't exist.
<ETX>= 0x03
<CRC>=
XOR among all the characters
following <STX>=(with exception
of <STX>), including the end
character <ETX> hexadecimally
encoded by two ASCII characters.
When a slave device is addressed by the master:
In case of reading request of the value contained in
a window, the slave answers a string equal to the
one sent by the master but in addition there is the
field
<DATA>
window.The format of the field <DATA> depends to
the window type.
The different types are:
Logic (L)
Numeric (N)
Alphanumeric (A)
Using the RS485 interface, the message structure
remains identical to the one used for the RS232/422
interface, the only difference being that the value
assigned to the ADDRESS <ADR> field in this case
can be any hex value, while for the RS 232/422 this
value must be set to 80 hex.
59
TECHNICAL INFORMATION
containing
the
value
Length
Characters
Permitted
1
'0'=OFF
'1'=ON
6
'-', '.','0'...'9'
(Justifield to the right
with '0')
max 10
' '...'_'
NOTE
87-900-855-01 (B)
of
the
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