The Mitsubishi QJ71MB91 is a MODBUS interface module for the MELSEC Q series, providing both RS-232 and RS-422/485 communication at data rates up to 115200 bps. It occupies 32 I/O points and draws 0.31 A from the 5V backplane, leaving plenty of headroom for additional I/O. Master and slave functions are both supported: the master side handles up to 32 slaves per channel via automatic communication (4K word buffers) or dedicated commands (up to 253 bytes per instruction), while the slave side offers 64K-point device sizes for coils, inputs, and registers, plus extended file registers up to 4086 K points. The module accepts one request per channel at a time. With a compact footprint of 9.8 x 2.74 x 9 cm, it fits neatly into the Q-series rack.
Typical lead time is 1–10 working days based on current supply channels.