15.1.2 Modes of Operation • Normal expanded wide mode Ports A and B are configured as a 16-bit multiplexed address and data bus and port E provides bus control and status signals. This mode allows 16-bit external memory and peripheral devices to be interfaced to the system. • Normal expanded narrow mode Ports A and B are configured as a 16-bit address bus and port A is multiplexed with 8-bit data. Port E provides bus control and status signals. This mode allows 8-bit external memory and peripheral devices to be interfaced to the system. • Normal single-chip mode There is no external expansion bus in this mode. The processor program is executed from internal memory. Ports A, B, K, and most of E are available as general-purpose I/O. • Special single-chip mode This mode is generally used for debugging single-chip operation, boot-strapping, or security related operations. The active background mode is in control of CPU execution andBDMfirmware is waiting for additional serial commands through the BKGD pin. There is no external expansion bus after reset in this mode. • Emulation expanded wide mode Developers use this mode for emulation systems in which the users target application is normal expanded wide mode. • Emulation expanded narrow mode Developers use this mode for emulation systems in which the users target application is normal expanded narrow mode. • Special test mode Ports A and B are configured as a 16-bit multiplexed address and data bus and port E provides bus control and status signals. In special test mode, the write protection of many control bits is lifted so that they can be thoroughly tested without needing to go through reset. • Special peripheral mode This mode is intended for Freescale Semiconductor factory testing of the system. The CPU is inactive and an external (tester) bus master drives address, data, and bus control signals.