User's Manual
39
•
To use this function, set REG23:bit 1 of all RS485 multi-dropped modems to 1. And
set all the RS485 Packet Interval (REG07) to different values more than 1.5 bytes
each. Further set this bit of the modem, the RS485 Packet Interval is set to the
longest, to 1.
Bit 1: RS485 collision avoidance
0
Invalid collision avoidance function (default value)
1
Use collision avoidance function
Table 5–24: Collision Avoidance Function
•
Sets to decide whether to use the collision avoidance function or not, together with
bit 2.
•
When modem tried to output a response or the received data, the modem outputs
only if RS485 line is available at the timeout of RS485 Packets Interval (REG07).
When RS485 line is not available at the timeout, the modem waits for a line becomes
available and starts re-measurement of its packet interval.
•
Set to 1 makes it unable to output neither response nor the received data, unless
other modem(s) outputs any data to the RS485 line and interval time measuring
becomes effect.
•
Bit 2 is used for the purpose of resolving this problem.
Bit 0: Global addressing command response
0
No P0 response to global addressing command (default value)
1
Respond P0 response to global addressing command
Table 5–25: Global addressing command response
•
Set to decide whether to return “P0” response (including “P1” for the transmit
command) to the terminal equipment for the global addressing command
(commands for Addresses 240 to 254).
•
When the global addressing command is issued to plural modems, which are
multi-dropped and have the same global address on RS485 line, there is a possibility
causing data collision on the RS485 line. Unless the RS485 Packet Interval is
properly set. This is because all modems return the “P0” (or P1) response to the
terminal equipment simultaneously on default memory setting. Such potential
problem can be avoided by limiting the modem to output the response to the global
addressing command is only one.