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AC Serial Communications Protocol
Appendix
Serial communication is accomplished either through the optional 9-pin Serial Communications Box or
through the USB port on the immersion circulator. If your operating system does not automatically recognize
the optional driver log on to: http://www.ftdichip.com/FTDrivers.htm for instructions.
Note This appendix assumes you have a basic understanding of communications protocols. Information on
the NC, STANDARD and NAMUR protocols is available upon request.
Note Keypad operation is still available with serial communications enabled.
Note NC protocol is required to use RS485 device addressing.
All commands must be entered in the exact format shown in the tables on the following pages. The tables
show all commands available, their format and responses. Controller responses are either the requested data
or an error message. The controller response must be received before the host sends the next command.
The host sends a command embedded in a single communications packet, then waits for the controller's
response. If the command is not understood, the controller responds with an error command. Otherwise, the
controller responds with the requested data.
Commands are not case sensitive. Upper or lower case letters may be used. Commands are listed in the
Commands Table, error responses are given in the Errors Table, and symbols are shown in the Key Table.
Key
Symbol
Meaning
[B]
A binary value 0 or 1 (0 = Off, FALSE or Disable(d); 1 = On, TRUE or Enable(d)).
[CR]
Carriage return – used as the termination character.
[U]
Text representing the units associated with a value.
[V]
A value that can be requested in a read command or sent as part of a set command.
[V
]
Maximum allowed value. Part of error message when set value is too high.
MAX
[V
]
Minimum allowed value. Part of error message when set value is too low.
MIN
Value: Read commands return analog [V] or bit [B] values or settings, while set commands send analog or bit
settings. Read commands return values in the same displayed precision. Set command messages missing
the space character between the command and the setting will be rejected, as the user's intent is unclear.
Units: A read command returning an analog [V] value or setting, will include the units [U] associated with that
value or setting. A set command sending an analog value will not include the units. The units returned by the
complementary read command are assumed.
Termination character: A carriage return [CR] is used to terminate command and response messages.
(Typically the "Enter" key on the keyboard.)
Note The inter-character timeout (time between transmitted characters) is set to30 seconds. Exceeding the
timeout will clear the receiver buffer and require the message to re retransmitted.
Note Special characters (backspace, delete, insert, etc.) are not recognized and generate error responses.
A-1
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