MC68HC11E0CFNE2 Datasheet, PDF (40/242 Pages) Freescale Semiconductor, Inc – M68HC11 CPU, Power-saving stop and wait modes, Low-voltage devices available (3.0–5.5 Vdc)

Operating Modes and On-Chip Memory
V_DD
MAX
690
V_DD
4.7 k
V_OUT
4.8-V
NiCd +
V_BATT
TO MODB/V_STBY
OF M68HC11
Figure 2-8. RAM Standby MODB/V_STBY Connections
The bootloader program is contained in the internal bootstrap ROM. This ROM, which appears as internal
memory space at locations $BF00–$BFFF, is enabled only if the MCU is reset in special bootstrap mode.
In expanded modes, the ROM/EPROM/OTPROM (if present) is enabled out of reset and located at the
top of the memory map if the ROMON bit in the CONFIG register is set. ROM or EPROM is enabled out
of reset in single-chip and bootstrap modes, regardless of the state of ROMON.
For devices with 512 bytes of EEPROM, the EEPROM is located at $B600–$B7FF and has the same read
cycle time as the internal ROM. The 512 bytes of EEPROM cannot be remapped to other locations.
For the MC68HC811E2, EEPROM is located at $F800–$FFFF and can be remapped to any 4-Kbyte
boundary. EEPROM mapping control bits (EE[3:0] in CONFIG) determine the location of the 2048 bytes
of EEPROM and are present only on the MC68HC811E2. Refer to 2.3.3.1 System Configuration Register
for a description of the MC68HC811E2 CONFIG register.
EEPROM can be programmed or erased by software and an on-chip charge pump, allowing EEPROM
changes using the single V_DD supply.
2.3.2 Mode Selection
The four mode variations are selected by the logic states of the MODA and MODB pins during reset. The
MODA and MODB logic levels determine the logic state of SMOD and the MDA control bits in the highest
priority I-bit interrupt and miscellaneous (HPRIO) register.
After reset is released, the mode select pins no longer influence the MCU operating mode. In single-chip
operating mode, the MODA pin is connected to a logic level 0. In expanded mode, MODA is normally
connected to V_DD through a pullup resistor of 4.7 kΩ. The MODA pin also functions as the load instruction
register LIR pin when the MCU is not in reset. The open-drain active low LIR output pin drives low during
the first E cycle of each instruction. The MODB pin also functions as standby power input (V_STBY), which
allows RAM contents to be maintained in absence of V_DD.
Refer to Table 2-1, which is a summary of mode pin operation, the mode control bits, and the four
operating modes.
M68HC11E Family Data Sheet, Rev. 5.1
40
Freescale Semiconductor