APS 6RL Series, Руководство по эксплуатации

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6RL SERIES OPERATION MANUAL
SECTION 7: REMOTE PROGRAMMING
Entire Contents Copyright
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2018 by Adaptive Power Systems, Inc. (APS) • All Rights Reserved • No reproduction without written authorization from APS.
6RL Series Regenerative DC Load Operation Manual Page 128 of 204
Code Error Explanation
0x05 5 CRC The CRC16 checksum at the end of the ModBus RTU message is wrong or
has been transmitted in wrong byte order (high byte first instead of low
byte)
0x07 7 Access denied Access to a certain register is not allowed or read only while trying
to write, or vice versa. The error also occurs when trying to write to a
writable address while the unit is not in remote control or in remote
control from a different interface
0x17 23 Unit in local Indicates, that write access to the unit is blocked by he "local" condition,
so only read access is possible. "Local" means that remote control is not
allowed.
An example: You attempted to switch the unit to remote in order to control it from PC, but
instead of an echo of your message, it returns something like this: 0x00 0x85 0x07 0x52 0x92.
This is an error message. The position of the function code contains the value 0x85.
According to the first table above, this is related to the function WRITE SINGLE COIL. The
error code in the message is 0x7 which means, according to the second table above, the
unit has denied the access. This can have different reasons, for example that the unit is
already in remote control via a different interface.
7.9.5 Examples of ModBus RTU messages
These examples can also be used for ModBus TCP, but they need to be extended by the
required ModBus TCP header and stripped from the unnecessary checksum.
1) Writing a Set value
Set values are adjustable limits for the physical values Current, Voltage, Power and
Resistance (where available). They can only be written to a unit if it has been switched to
remote control before via a digital interface.
Example: You want to set the current to 50%. According to the register lists, the “Set current
value” is at address 501 (0x1F5) and assigned function is WRITE Single Register. Expecting
the unit be already in remote control mode, the message to build then has to be like this:
Addr FC Start Data CRC
0x00 0x06 0x01F5 0x6666 0x325F
Response:
Addr FC Start Data CRC
0x00 0x06 0x01F5 0x6666 0x325F
In this case, the unit is expected to return an echo of your message, indicating successful
execution of the command. The display of the unit should now show 50% of the maximum
current of your unit. For a DC load with 510 A nominal input current, it should show 255.0 A
or for a model with 170 A current rating, it should show 85 A.
2) Query all actual values at once
The unit holds three readable actual values of voltage, current and power. Electronic loads
feature an additional actual resistance value in their displays, which cannot be read via