ICS ELECTRONICS 4809A, Instruction Manual

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3-22
3
TABLE 3-5 MODBUS COMMANDS CONT'D
Syntax Meaning
WF reg, num Write Floating Point Value Command (0x16). Writes an
IEEE 754 single precision 32-bit value to two registers
in low word to high word order. reg specifies the low
word. reg +1 is the high word. num is determined by
the parameter being controlled and can range from 2
127
to 2
-127
L[?] w Loopback Command (code 0x08). Writes a 16-bit word,
w , out to a Modbus device and returns a single response
word to the GPIB bus. The question mark is optional
for smart programs.
(4)
Value for w is 0 to 65535.
D time Timeout Command. Sets timeout value of Modbus
response message in milliseconds. Timeout is the total
time for the message to be received by the 48x9A. Value
for time is 1 to 65,535 milliseconds. The default value
is 100.
D? Queries the current timeout setting.
E? Read Error Command. Reads and clears the Modbus
Error Register and bit 6 in the Event Status Register.
Returns a error code whose value is 0 to 255. Current
error values are:
0 No errors present
1 Exception Code 1
2 Exception Code 2
3 Exception Code 3
100 CRC Error
101 Timeout Error indicates no characters
received in the response message.
2nn Partial or corrupted message received.
where nn is the number of received bytes.
Notes:
1. All values are in decimal. To enter HEX values, the value must be preceded with
a #h . i.e. 100 decimal = #h64. Integer range is 0 to 65535.
2. Response parameter format set by SCPI FORMat command. Default is ASCii
3. Do not combine the Modbus commands in Table 3-5 with IEEE-488.2
commands or SCPI commands to avoid query errors or otherwise confusing the
GPIB<->Modbus Interfaces.
4. The [?] is an optional symbol for smart programs like ICS’s GPIBKybd program.
These programs can recognize the command as a query and automatically read the
response
.