Hanna Instruments HI 504 - Manual (Page 31)

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Following is the complete list of commands available:
Command Parameter Remarks
NNMDR not available Requests firmware code
(always available)
NNHOP not available Requests hardware options
NNSNR not available Requests hardware identifier
(always available)
NNSTS not available Requests instrument status
(relays, LEDs, configuration
change flag, etc.)
NNPHR not available Requests last pH reading
(instrument configured for pH)
NNMVR not available Requests last mV reading
(always available)
NNTMR not available Requests temperature reading
(instrument configured for pH)
NNCAR not available Requests all last calibration data
(always available)
NNGET CNN Requests setup item C.NN.
Use the NNSNR command if
hardware identifier is needed.
(NNGET command is
answered with
“”
for the hardware identifier)
NNPWD C
1
C
2
C
3
C
4
Sends the general password
(always available)
NNSET CNNP
1
P
2
C
1
C
2
C
3
C
4
Sets setup item C.NN with
parameter P
1
P
2
C
1
C
2
C
3
C
4
(*)
(not available in setup mode)
NNEVF not available Requests event log file
(available in idle, event
scrolling or last calibration data
scrolling mode w/control OFF)
Line conditions, pull-up and pull-down resis-
tors should be connected as shown.
The Fail-Safe resistors are connected only to
one unit in the line, and their value depends
on the application and characteristic imped-
ance of the connection cable.
The GND pin of the interface connector and all the interface
signals are optoisolated from the ground of the instrument,
the electrode and the temperature sensor.
Before connecting the meter to the computer, consult the com-
puter manual.
The process controller can only work as a slave component.
In other words it can work as a remote terminal equipment
answering to the commands only.
RS485 PROTOCOL FOR HI 504
Commands are composed of four parts: addresses, com-
mand identifier, parameter, end of command.
Some commands are used when the master is requesting
information from the controller, other when the master wants
to set a parameter in the process memory (RAM or EEPROM).
The end of commands corresponds to the CR char (0x0d).
The master software must send the command string with a
maximum delay of 20ms between each character.
The program on the master must not allow setting commands
other than keyboard or cleaning start/stop commands if the
general password has not been entered. After the general
password recognition through the “PWD” command, a 1-
minute time-out is let before the process meter locks again,
i.e. if the PC program waits for more than 1 minute between
two subsequent setting commands, the second one is not
fulfilled and the “PWD” command must be issued again.