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Communication Protocol
The communication protocol is a MASTER/SLAVE
type where:
• Host = MASTER
• Controller = SLAVE
The communication is performed in the following
way:
1. the host (MASTER) send a MESSAGE + CRC to
the controller (SLAVE);
2. the controller answer with an ANSWER + CRC
to the host.
The MESSAGE is a string with the following format:
<STX>+<ADDR>+<WIN>+<COM>+<DATA>+<ETX>
+<CRC>
where:
NOTE
When a data is indicated between two quotes ('...')
it means that the indicated data is the correspond-
ing ASCII character.
− <STX> (Start of transmission) = 0x02
− <ADDR> (Unit address) = 0x80 (for RS 232)
<ADDR> (Unit address) = 0x80 + device num-
ber (0 to 31) (for RS 485)
− <WIN> (Window) = a string of 3 numeric char-
acter indicating the window number (from '000'
to '999'); for the meaning of each window see
the relevant paragraph.
− <COM> (Command) = 0x30 to read the window,
0x31 to write into the window
− <DATA> = an alphanumeric ASCII string with
the data to be written into the window. In case
of a reading command this field is not present.
The field length is variable according to the
data type as per the following table:
DATA TYPE
FIELD
LENGTH
Logic (L)
1
Numeric (N)
6
Alphanumeric (A)
10
− <ETX> (End of transmission) = 0x03
− <CRC> = XOR of all characters subsequent to
<STX> and including the <ETX> terminator.
The value is hexadecimal coded and indicated
by two ASCII character.
VALID
CHARACTERS
'0' = OFF
'1' = ON
'-', '.', '0' . . . '9' right
justified with '0'
from blank to '_' (ASCII)
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TECHNICAL INFORMATION
The addressed SLAVE will respond with an
ANSWER whose structure depends from the
MESSAGE type.
When the MESSAGE is a reading command, the
SLAVE will respond transmitting a string with the
same structure of the MESSAGE.
NOTE
Some error settings are foreseen:
0x15 NACK
0x32 UNKNOWN WINDOW
0x33 BAD DATA TYPE
0x34 OUT OF RANGE
0x35 BAD OPERATION
NOTE
Using the RS 485 interface, the message structure
remains identical to the one used for the RS 232
interface, the only difference being that the value
assigned to the ADDRESS <ADDR>
The controller can answers with the following re-
sponse types:
TYPE
LENGTH
VALUE
Logic
1 byte
Numeric
6 bytes
Alphanumeric
10 bytes
ACK
1 byte
NACK
1 byte
Unknown
1 byte
Window
Data Type
1 byte
Error
Out of Range
1 byte
Win Disabled
1 byte
NOTE
The RS-485 is a 2-wire (gnd optional) half-duplex
communication link.
foreseen with
Read/Write com-
mands
foreseen only
with Write com-
mands
DESCRIPTION
After a read instruction
-
of a logic window
After a read instruction
-
of a numeric window
After a read instruction
-
of an alphanumeric
window
The command execu-
(0x6)
tion has been success-
fully completed
The command execu-
(0x15)
tion has been failed
The specified window
(0x32)
in the command is not
a valid window
The data type specified
in the command (Logic,
Numeric or Alphanu-
(0x33)
meric) is not accorded
with the specified Win-
dow
The value expressed
during a write com-
(0x34)
mand is out of the
range value of the
specified window
The specified window
is Read Only or tempo-
rarily disabled (for ex-
(0x35)
ample you can't write
the Soft Start when the
Pump is running)
87-901-011-01
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