
Chapter 8 - Appendices
8 - 8
584S Frequency Inverter
Valid Response of the 584S to this Message
Valid Response of the 584S to this Message
Valid Response of the 584S to this Message
Valid Response of the 584S to this Message
After the message has been sent, the computer adopts slave status and expects to receive a reply from the 584S. In so doing,
the 584S assumes Master status and, providing the 584S has successfully received the message in full, it responds in the
following form:
(STX)
(C1)
(C2)
(D1)
(D2)
(D3)
(Dn)
(ETX)
(BCC)
which constitutes a message defined as:
(STX)
Start of text.
(C1)(C2)
Parameter specified by mnemonic.
(D1 to Dn)
Value of the requested parameter (string may be of any length as determined by the
data). The 584S responds with the shortest message which represents the data value.
If the data value is an integer then it does not send a decimal point. Trailing zeros in
the decimal part are not sent.
(ETX)
End of text.
(BCC)
Block check character which is the character generated by taking the exclusive OR of
the ASCII values of all the characters transmitted after and excluding (STX) up to and
including (ETX).
e.g. if a message with (D1 - Dn) is 5 characters (BCC) = (C1) EOR (C2) EOR (D1)
EOR (D2) EOR (D3) EOR (D4) EOR (D5) EOR (ETX)
where EOR = Exclusive OR
The computer must check this (BCC) before accepting this reply as valid. Also the software must be able to extract the
number from the data string taking into account the protocol of the data transmission.
NOTE: If the 584S receives the message but does not recognise the mnemonic it will respond with (EOT).
The (EOT) hands back control to the computer.
Further Enquiry and Termination
Further Enquiry and Termination
Further Enquiry and Termination
Further Enquiry and Termination
The computer then assumes master status again and three options are available:
1.
Repeat Parameter Facility (NAK). If the computer transmits a (NAK) after the valid reply, it causes the 584S to repeat
the parameter that was just received. This allows continuous monitoring of the same parameter without having to
re-establish the connection.
2.
Scroll Mode Facility (ACK). If the computer transmits an (ACK) after a valid 'reply', it causes the 584S to fetch the
next parameter from the parameter list. This facility enables the computer to sequence continuously through all the
parameters of the 584S.
3.
Terminate Communication (EOT). The termination procedure is entered when the selection of a particular instrument
is no longer required or when a 584S does not respond to a message or replies with an (EOT) character. The
computer assumes Master status and transmits an (EOT) character to enable all the instruments on the data link to
respond to the next GID-UID address parameter.
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Summary of Contents for 584S
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