0xFD00 (Modbus holding register 0xFD01), which can therefore be accessed via Modbus holding register 0x0D01 (332910) when register remapping is enabled.

When register remapping is enabled, only accesses to Modbus registers 0x0A01 – 0x1000 are affected: the normal locations for the critical control and status registers remain unaffected and can still be accessed (i.e. Communication Frequency Command will be updated via writes to either register 0x0A02 or 0xFA02: both will write to ASD register 0xFA01).

Refer to section 11.2 for further information regarding configuration of the register remap selection.

10.5 ASD Scan Registers

Scan registers are used to define ASD registers that the user wishes to access quickly. ASD registers that are configured to be scan registers will have their data mirrored locally on the ETH-100. Requesting the data from or writing data to an ASD register that is set up to be a scan register will take less network time because the ETH-100 simply accesses a local value instead of initiating a transaction with the ASD to process the data.

Refer to section 11.3.2 for further information regarding configuration of the scan registers.

10.6 Modbus Programmable Pointer Registers

Programmable pointer registers (PPR) allow the user to access non-consecutive Modbus registers with only one Modbus transaction. Modbus register locations 0xFC00 ~ 0xFC0F are reserved by the ETH-100 to access the registers defined in the PPR section of the "channels" page of the ETH-100's embedded web server. For example, if you would like to continuously read the data from ASD registers 0xFD00, 0xFE01, 0xFE04 and 0xFE05, the standard Modbus register configuration would require 3 read commands to be issued: one reading 1 Modbus register starting at register 0xFD01, one reading 1 Modbus register starting at register 0xFE02, and one reading 2 Modbus registers starting at register 0xFE05. To conserve network bandwidth and speed processing time, however, the programmable pointer registers can be used to allow the same information to be accessed, but by only issuing 1 command which reads 4 Modbus registers.

To configure this function, enter the register numbers of the Modbus registers you would like to continuously access into the PPR section of the embedded web server's "channels" page (refer to section 11.3.3). For example, we could set PPR register location 0xFC00 to a value of 0xFD01 (the first Modbus register number we want to access), register location 0xFC01 to a value of 0xFE02, register location 0xFC02 to a value of 0xFE05, and register location 0xFC03 to a value of 0xFE06. The 4 registers that are to be monitored can now be accessed simply by issuing 1 Modbus holding register read command with a length of 4 starting from Modbus register location 0xFC00. The returned data will be the data obtained from ASD registers 0xFD00, 0xFE01, 0xFE04, and 0xFE05 (in that order). IMPORTANT: Note that PPR values refer to MODBUS registers. That is, Modbus registers = ASD registers + 1.

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