Dual-port serial interface for Q Series backplane
The QJ71C24N mounts in any Q Series base slot and occupies 32 I/O points on the MELSEC network map. One RS232 port handles point-to-point computer link or programming connection; the second port supports RS485/RS422 with multidrop for daisy-chaining multiple devices on the same twisted pair. Baud rate tops out at 230400 bps on the RS232 channel and 115200 bps on the multidrop channel — enough for polled RTU protocols or Mitsubishi's own computer link. The 27.4 mm width fits a single slot, leaving the rest of the rack for I/O or motion modules.