Agilent Technologies 969-8888, Instruction Manual

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TECHNICAL INFORMATION
89/107 87-901-011-01
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
M CRC
to
the controller (SLAVE);
2. the controller answer with an
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
VALID
CHARACTERS
Logic (L) 1 ‘0’ = OFF
‘1’ = ON
Numeric (N) 6 ‘-‘, ‘.’, ‘0’ . . . ‘9’ right
justified with ‘0’
Alphanumeric (A) 10 from blank to ‘_’ (ASCII)
−
<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.
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
foreseen with
Read/Write com-
mands
0x33 BAD DATA TYPE
0x34 OUT OF RANGE
0x35 BAD
OPERATION
foreseen only
with Write com-
mands
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 DESCRIPTION
Logic 1 byte -
After a read instruction
of a logic window
Numeric 6 bytes -
After a read instruction
of a numeric window
Alphanumeric 10 bytes -
After a read instruction
of an alphanumeric
window
ACK 1 byte (0x6)
The command execu-
tion has been success-
fully completed
NACK 1 byte (0x15)
The command execu-
tion has been failed
Unknown
Window
1 byte (0x32)
The specified window
in the command is not
a valid window
Data Type
Error
1 byte (0x33)
The data type specified
in the command (Logic,
Numeric or Alphanu-
meric) is not accorded
with the specified Win-
dow
Out of Range 1 byte
(0x34)
The value expressed
during a write com-
mand is out of the
range value of the
specified window
Win Disabled 1 byte (0x35)
The specified window
is Read Only or tempo-
rarily disabled (for ex-
ample you can’t write
the Soft Start when the
Pump is running)
NOTE
The RS-485 is a 2-wire (gnd optional) half-duplex
communication link.