Delta Electronics ASDA-AB Modbus Communication Protocol, „ Code Description Ascii Mode, RTU Mode

Chapter 8 MODBUS CommunicationsASDA-AB Series

8.3MODBUS Communication Protocol

When using RS-232/485/422 serial communication interface, each ASDA-AB series AC servo drive has a pre-assigned communication address specified by parameter “P3-00”. The computer then controls each AC servo drive according to its communication address. ASDA-AB series AC servo drive can be set up to communicate on a MODBUS networks using on of the following modes: ASCII (American Standard Code for Information Interchange) or RTU (Remote Terminal Unit). Users can select the desired mode along with the serial port communication protocol in parameter “P3-02”.

„Code Description:

ASCII Mode:

Each 8-bit data is the combination of two ASCII characters. For example, a 1-byte data: 64 Hex, shown as ‘64’ in ASCII, consists of ‘6’ (36Hex) and ‘4’ (34Hex).

The following table shows the available hexadecimal characters and their corresponding ASCII codes.

Character	‘0’	‘1’	‘2’	‘3’	‘4’	‘5’	‘6’	‘7’
ASCII code	30H	31H	32H	33H	34H	35H	36H	37H
Character	‘8’	‘9’	‘A’	‘B’	‘C’	‘D’	‘E’	‘F’
ASCII code	38H	39H	41H	42H	43H	44H	45H	46H

RTU Mode:

Each 8-bit data is the combination of two 4-bit hexadecimal characters. For example, a 1-byte data: 64 Hex.

„Data Format:

10-bit character frame (For 7-bit character)
7N2	Start
			0	1	2			3		4	5	6	Stop	Stop
		bit											bit	bit
									7-data bits
7E1						10-bits character frame
	Start												Even
			0	1	2			3		4	5	6		Stop
		bit											parity	bit
								7-data bits
7O1							10-bits character frame
	Start		0	1	2			3		4	5	6	Odd	Stop
		bit											parity	bit

7-data bits

10-bits character frame

Revision January 2009 8-9