M Series AC Servo
User Manual
146
Rev. 1.0
7/31/2019
400-820-9661
Two-Wire Configuration
In a 2-wire system, the host must disable its transmitter before it can receive data. This must be done
quickly before a drive begins to answer a query. The M2 drive includes a transmit delay parameter that
can be adjusted to compensate for a host that is slow to disable its transmitter. This adjustment can be
made over the network using the TD command, or it can be set using the M servo suite software. It is not
necessary to set the transmit delay in a four wire system.
NOTE: For RJ45 crystal connector, we recommend standard CAT5 cables.
9.3 ModBUS/RTU Communication
There are two types of communication methods for ModBUS, ASCII(American Standard Code for
information interchange) mode and RTU(Remote Terminal Unit)mode, this is defined based on different
bus modulation and demodulation methods. For M2 series AC servo drives, only ModBUS RTU is
supported.
9.3.1 Data Encode
Big-endian: The most significant byte (MSB) value is stored at the memory location with the lowest
address; the next byte value in significance is stored at the following memory location and so on. This is
akin to Left-to-Right reading in hexadecimal order.
For example: To store a 32bit data 0x12345678 into register address 40031 and 40032. 0x1234 will be
defined as MSB, and 0x5678 as LSB. With big-endian system
Register 40031 = 0x1234
Register 40032 = 0x5678
When transfer 0x12345678, the first word will be 0x1234, and the second word will be 0x5678
Little-endian: The most significant byte (MSB) value is stored at the memory location with the highest
address; the next byte value in significance is stored at the following memory location and so on. This is
akin to Left-to-Right reading in hexadecimal order.
For example: To store a 32bit data 0x12345678 into register address 40031 and 40032. 0x5678 will be
defined as MSB, and 0x1234 as LSB. With little-endian system
Register 40031 = 0x5678
Register 40032 = 0x1234
When transfer 0x12345678, the first words will be 0x5678, and the second words will be 0x1234
M2 drive parameter P-75 (PR) defines data transfer type
P-75 (PR) = 5 represents Big-Endian
P-75 (PR) = 133 represents Little-Endian
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