MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor 25
Chapter 2 Memory

2.1 Introduction

The central processor unit (CPU08) can address 64 Kbytes of memory space. The memory map, shown
in Figure 2-1, includes:
32 Kbytes of FLASH
768 bytes of random-access memory (RAM)
46 bytes of user-defined vectors
240 bytes of monitor read-only memory (ROM)

2.2 Unimplemented Memory Locations

Some addresses are unimplemented. Accessing an unimplemented address can cause an illegal address
reset. In the memory map and in the input/output (I/O) register summary, unimplemented addresses are
shaded.
Some I/O bits are read only; the write function is unimplemented. Writing to a read-only I/O bit has no
effect on microcontroller unit (MCU) operation. In register figures, the write function of read-only bits is
shaded.
Similarly, some I/O bits are write only; the read function is unimplemented. Reading of write-only I/O bits
has no effect on MCU operation. In register figures, the read function of write-only bits is shaded.

2.3 Reserved Memory Locations

Some addresses are reserved. Writing to a reserved address can have unpredictable effects on MCU
operation. In the memory map (Figure 2-1) and in the I/O register summary (Figure 2-2) reserved
addresses are marked with the word reserved.
Some I/O bits are reserved. Writing to a reserved bit can have unpredictable effects on MCU operation.
In register figures, reserved bits are marked with the letter R.