The MC68CK338, a highly-integrated 32-bit microcontroller, combines high-performance data manipulation capabilities with powerful peripheral subsystems. The MCU is built up from standard modules that interface through a common intermodule bus (IMB). Standardization facilitates rapid development of devices tailored for specific applications. The MCU incorporates a low-power 32-bit CPU (CPU32L), a low-power system integration module (SIML), a queued serial module (QSM), and a configurable timer module 6 (CTM6). The MCU clock can either be synthesized from an external reference or input directly. Operation with a 32.768 kHz reference frequency is standard. The maximum system clock speed is 14.4 MHz. System hardware and software allow changes in clock rate during operation. Because MCU operation is fully static, register and memory contents are not affected by clock rate changes. High-density complementary metal-oxide semiconductor (HCMOS) architecture and 3V nominal operation make the basic power consumption of the MCU low. Power consumption can be minimized by either stopping the system clock, or alternatively, stopping the system clock only at the CPU32L, and allowing the other modules to continue operation. The CPU32 instruction set includes a low-power stop (LPSTOP) command that allows either of these power saving modes. The CTM6 includes new features such as a port I/O submodule, a 64-byte RAM submodule and a real time clock submodule.