High levels of integration in integrated circuits often lead to the problem of running out of pins. Narrow data buses can be used to alleviate this problem provided that the degraded performance due to wait cycles can be tolerated. We address bus coding methods for low-power core-based systems incorporating narrow buses. We show that transition signaling combined with bus-invert coding, which we call BITS coding, is particularly suitable for the data patterns of typical DSP applications on narrow data buses. The application of BITS coding to real circuit design is limited by the extra bus line introduced, which changes the pinout of the chip. We propose a new coding method, which does not require the extra bus line but retains the advantage of BITS.