We had proposed a novel CDMA based bus interface which features multi-bit simultaneous data transmission as a short range bus interface. This paper explores the limitation of CDMA bus interface, in terms of its coupling noise immunity based on a first order mathematical BER model. Besides coupling noise, other physical effects of circuit implementation such as process variation and clock skews have been considered. The simulation results at 50 MHz yields that using code length of 128, MB-CDMA bus interface is capable of 60 parallel transmission of 3-bits data, achieving 70 Mbps transmission which is larger than conventional TDMA based Sonic bus. The above result, obtained under random coupling noise with 2 times transmitting signal amplitude, reveals bit error rate below 10/sup -20/.