Amtech
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3. Data Access
3.1 Register Read and Write
The device parameter and data set information is mapped into a 4xxxx register area. This holding
register area can be read from an external device, and an external device can modify the register
values by writing to them.
All parameters have access for either reading or writing. The parameter writes are verified for correct
value, and for valid register addresses. Some parameters never allow writes, some parameters allow
write, and some can be modified at any time.
The register addresses that are not allocated to any device parameter or data set are invalid. No
reads or writes are allowed for these addresses. If there is an attempt to read or write outside the
parameter addresses, the Modbus interface will return an exception code to the controller.
Exception Codes
Below is the table of exception code generated by slave device.
01 ILLEGAL FUNCTION Unsupported Command.
02 ILLEGAL DATA ADDRESS Address does not exist or is read/write protected.
03 ILLEGAL DATA VALUE Value is outside min-max limits. Parameter is read-only.
04 SLAVE DEVICE FAILURE Reading a multiple parameter register, which includes one or
more read protected parameters.
06 SLAVE DEVICE BUSY Slave device performing other important operation and it
cannot give response. Try with query after sometime.
3.2 Data Update
The device designed for time-optimized, reliable data transfer between the Modbus network and the
master device.
This device supports three function codes of the general modbus protocol. They are as below.
03 Read Holding Registers Read the binary contents of holding registers (4X
references) in the slave.
06 Preset Single Register Presets a value into a single holding register (4X reference).
When broadcast, the function presets the same register
reference in all attached slaves.
16 (10 Hex) Preset Multiple Regs Presets values into a sequence of holding registers (4X
references). When broadcast, the function presets the same
register references in all attached slaves.
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