The proposed multi-band multi-modulation I/O (MMI) for mobile memory interface consists of two RF-band and 4-PAM (pulse-amplitude modulation) transceivers for simultaneous bidirectional read/write operations on a shared single-ended 5 cm off-chip transmission line. A novel band-selective transformer is introduced to combine and split two amplitude shift keying modulated RF-bands with a 4-PAM baseband for transmitting and receiving multiple data concurrently. The MMI interface consumes 2.8 pJ/b from a 1.2 V supply voltage. Testing results show that the MMI interface achieves an overall data rate of 14 Gb/s/pin. It is implemented in a 65 nm CMOS process with chip area of 0.25 mm².