Freescale Semiconductor MC68HC908MR32 - Manual (Page 25)

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.