Alpha Omega Instruments 800 Series User Manual

MODBUS COMMANDS OVER GPIB
Read Error Command. Reads the Modbus Error Register. Returns an
error code whose value is 0 to 255.
0 = No errors.
1,2,3 = Exception code #.
100 = CRC error.
101 = Timeout error (no characters received)
2nn = Partial or corrupted with nn bytes received.
-
E?
Queries the current timout setting.-
D?
Timeout Command. Sets timeout value of Modbus response message
in milliseconds. Timeout is the total time for the message to be received
by the controller. Value for time is 1 to 65535 milliseconds.
Leave this at the default of 100.
100
D time
Write Block command. Writes multiple 16 bit words, w(i) to multiple
registers. Starting register, reg. Number, num specifies how many words
are to be written. Values for reg are 0 to 32767. Values for num are 1 to
64. Values for w are 0 to 65535.
-
WB reg, num,
w(0)..w(n)
Write Register Command. Writes a 16 bit value, w to a single Modbus
device register, reg. Values for reg are 0 to 32767. Values for w are 0 to
65535. An example is:
W 100, 55 writes the decimal value 55 to 100.
Recommended write command. Check for proper write by reading back
the register with the “R” command above. See WARNING about the
Non-volatile memory on page 102.
-
W reg, w
Read Register Command. Reads one or multiple Modbus device
registers. User specifies starting register reg and number of registers to
be read num. The [?] is an optional symbol. Values for reg are 0 to
32767. Values for num are 1 to 64. Responses are returned as 16 bit
decimal or HEX values separated by commas. Output format selected
with the Format command. I.e.
R? 300,1 reads the set point
R? 100,1 reads the actual process temperature.
R? 713,3 reads the current limit registers 713, 714, & 715.
-
R [?] reg, num
Loopback Command.-
L [?] w
Modbus Address Command. This must match the setting programmed
at the front panel of the controller. Default=1.
1
C addr
MeaningDefaultSyntax
ALPHA OMEGA INSTRUMENTS CORP. Instruction Manual
Series 800/850 Thermoelectric Cooler Controller Page 88

Alpha Omega Instruments 800 Series Specifications

General

Brand	Alpha Omega Instruments
Model	800 Series
Category	Controller
Language	English