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.

MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1

Freescale Semiconductor

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Freescale Semiconductor MC68HC908MR16 manual Chapter Memory, Unimplemented Memory Locations, Reserved Memory Locations
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MC68HC908MR16, MC68HC908MR32 specifications

Freescale Semiconductor's MC68HC908MR32 and MC68HC908MR16 microcontrollers are part of the popular HC08 family, designed primarily for embedded applications. These microcontrollers are particularly favored in automotive, industrial, and consumer product sectors due to their reliability and versatility.

One of the standout features of the MC68HC908MR series is its CMOS technology, which enhances performance while minimizing power consumption. This makes these microcontrollers suitable for battery-operated devices. They operate at a maximum clock frequency of 2 MHz and offer a 16-bit architecture, providing a solid balance between processing power and efficiency.

The MC68HC908MR32 variant is equipped with 32KB of flash memory, which allows for the storage of complex programs and extensive data handling. In contrast, the MC68HC908MR16 features 16KB of flash memory, making it ideal for simpler applications. Both microcontrollers also come with 1KB of RAM, enabling efficient data processing and real-time operations.

Another significant characteristic of these microcontrollers is their integrated peripherals. They come with multiple input/output (I/O) pins, which allow for connectivity with various sensors and actuators. The built-in timer systems offer precise timing control for automotive and industrial applications, while the Analog-to-Digital Converter (ADC) provides essential conversion capabilities for various analog signals.

For communication purposes, the MC68HC908MR series includes a serial communication interface, enabling easy integration with other devices and systems. This versatility facilitates the development of complex systems that require interaction with external components.

Security is another crucial aspect of these microcontrollers. They have built-in fail-safe mechanisms to ensure reliable operation under various conditions, making them suitable for critical systems. Additionally, their robust architecture helps to safeguard against potential disruptions or attacks.

In summary, Freescale Semiconductor's MC68HC908MR32 and MC68HC908MR16 microcontrollers are key players in the embedded systems landscape. Their blend of power efficiency, integrated features, and scalability ensures they remain relevant for a wide array of applications, making them a favored choice among engineers and developers looking for dependable solutions in a competitive market.
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