CHAPTER 13 RS-485 COMMUNICATIONS
PC Loader Communications 13-43
13
13.2.8 Communications Starting Procedure
The amplifier does not respond to the host until power is turned on and the internal initialization process
is finished. Conduct the following procedure at power-on, and then start regular communications.
(1) After the amplifier is turned on, wait for about 1.5 s.
(2) The host issues any command and checks if the amplifier responds.
At the time, the "status data (STR1)" in the response data is checked if "completion of power-on
initialization (bit 3)" is 0 (OFF). If the bit is 1 (ON), initialization is in progress.
13.2.9 Regular Communications Procedure
(1) The host sends a transmission message to the amplifier.
(2) When receiving a transmission message, the amplifier processes the transmission message and
sends back a response message.
The host sends the next transmission message after checking the response message. Do not send
the transmission message without checking the response message.
(3) The amplifier is constantly in command state from the host unless process (2) is in progress.
[Example of processing procedure upon an error for improvement of reliability]
(1) Transmission error at physical or character level (detected by amplifier)
If a transmission error at the physical or character level (such as a parity error) is caused during
reception of a transmission message sent from the host, the amplifier does not send back the
response message (considered as nonresponse).
If there is no response from the amplifier, the host should send the same transmission message
again.
The timer for judging absence of response (time-out) is counted after transmission of the
transmission message is finished.
Time-out period shall be as below according to the transmission speed.
Parameter interrupt command Other commands
115200 bps: 250 ms or over 100 ms or over
38400 bps: 250 ms or over 100 ms or over
19200 bps: 350 ms or over 200 ms or over
9600 bps: 550 ms or over 400 ms or over
The retry frequency depends on each application, but recommend being more than twice.
(2) Transmission error at physical or character level (detected by host)
If there is a transmission error at the physical or character level during reception of a response
message from an amplifier, the host should send the same transmission message again.
Re-transmission should be performed after the following timing after the transmission error.
115200 bps: 50 ms or over
38400 bps: 50 ms or over
19200 bps: 100 ms or over
9600 bps: 200 ms or over
The retry frequency depends on each application, but recommend being more than twice.
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