User Manual of EM760 High-Performance Inverter Table 10-5 Correspondence between Time Interval and Baud Rate (t adjust =1ms) Fig. 10-4 Schematic Diagram ofNormal and Exceptional Data Frames 10.4.2 Data frame processing Upon receiving a frame data, the system will first perform preprocessing to determine whether it is a legal frame sent to this machine and check whether the data is correct, followed by final processing. If the received frame is not legal, the data will not be sent back. If the received frame is legal but incorrect, the corresponding exceptional message frame will be sent back. Legal frame: Meet the address (local or broadcast) and length (not less than 3) requirements.
Correct frame: It is a legal frame with a correct memory address. The memory content is within the defined range and can be processed at present. 10.4.3 Response delay The response delay (depending on the function code F10.04) is defined as the time interval from the reception ofvalid data frame [7] (data in the RS-485 network, different from the command sent by the keyboard) to data parsing and return. Since the starting and ending characters are defined in the standard protocol, it is impossible to avoid response delay, at least “3.5-character time interval + 1 ms (chip stabilization time of 485 protocol, t wait2 )”. The specific minimum time interval is related to the baud rate.
If the baud rate is 9600bps, the minimum response delay is 5ms (3.5Ч10/9600+1=4.64≈5). If the communication data involves EEPROM operation, the time interval will be longer. [ 7 ]: Valid dataframe: Sent by the external master station (not keyboard) to this machine. The function code, length and CRC of the data are correct. 273 Baud rate (bps) Starting and ending time interval T interval (t ) adjust Exception interval T exception (t ) adjust Remarks 4800 8 4 The idle level of 3ms or less is allowed for a normal frame. When the idle level is 8ms or greater, it indicates the end of a frame of data. 9600 4 2 The idle level of 1ms or less is allowed for a normal frame.
When the idle level is 4ms or greater, it indicates the end of a frame of data. 19200 2 1 The idle level ofless than 1ms is allowed for a normal frame. When the idle level is 2ms or greater, it indicates the end of a frame of data. Higher 1 1 When an idle level of 1ms appears, it indicates the end of a frame.