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APPENDIX
B
Serial Communications
The different AC motor drive parameters can be programmed and displayed by remote control
via the RS-485 serial interface. A personal computer may be used to load, change, or monitor
the parameter value through the PC‘s RS-485 interface, which permits communication with
higher-level automation systems. This appendix describes the following:
Computer Control
Data Format and Protocol
Character Delay Time and Response Delay Time
Computer Control
The VFD-A series AC motor drive has a built in RS-485 serial communication port on its control
terminal block marked SG+, SG-. The two connector pins are defined as follows:
SG ＋ : Signal ＋
SG－ : Signal －
Each VFD-A AC motor drive has a pre-assigned slave address specified by Pr.-78. The computer
may select any AC drive according to this slave address. The computer may also control all of the
AC drives connected to it when the “A” code in command string is 02H.
Data Format and Protocol
Data Format
Baud Rate (Transmission speed in bits per second)
Range of values: 1200, 2400, 4800 Baud (See Pr.-77)
Eleven (11) bits are required to represent each character, as shown in the following
example:
Number of bits Function
1 start bit
8 data bits
1 odd parity bit
1 stop bit
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