Development Support

Features include:

•Normal user-mode pin functionality

•One pin dedicated to serial communication between monitor ROM and host computer

•Standard mark/space non-return-to-zero (NRZ) communication with host computer

•4800 baud–28.8 Kbaud communication with host computer

•Execution of code in random-access memory (RAM) or ROM

•FLASH programming

18.3.1 Functional Description

The monitor ROM receives and executes commands from a host computer. Figure 18-8shows a sample circuit used to enter monitor mode and communicate with a host computer via a standard RS-232 interface.

Simple monitor commands can access any memory address. In monitor mode, the MCU can execute host-computer code in RAM while all MCU pins retain normal operating mode functions. All communication between the host computer and the MCU is through the PTA0 pin. A level-shifting and multiplexing interface is required between PTA0 and the host computer. PTA0 is used in a wired-OR configuration and requires a pullup resistor.

18.3.1.1 Entering Monitor Mode

There are two methods for entering monitor:

•The first is the traditional M68HC08 method where VDD + VHI is applied to IRQ1 and the mode pins are configured appropriately.

•A second method, intended for in-circuit programming applications, will force entry into monitor mode without requiring high voltage on the IRQ1 pin when the reset vector locations of the FLASH are erased ($FF).

NOTE

For both methods, holding the PTC2 pin low when entering monitor mode causes a bypass of a divide-by-two stage at the oscillator. The CGMOUT frequency is equal to the CGMXCLK frequency, and the OSC1 input directly generates internal bus clocks. In this case, the OSC1 signal must have a 50 percent duty cycle at maximum bus frequency.

Table 18-1is a summary of the differences between user mode and monitor mode.

Table 18-1. Mode Differences

 

 

 

Functions

 

 

 

 

 

 

 

Modes

 

 

 

 

 

 

 

 

 

 

 

COP

Rest

Reset

 

Break

Break

SWI

SWI

 

Vector High

Vector Low

 

Vector High

Vector Low

Vector High

Vector Low

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

User

Enabled

$FFFE

$FFFF

 

$FFFC

$FFFD

$FFFC

$FFFD

 

 

 

 

 

 

 

 

 

 

 

 

Monitor

Disabled(1)

$FEFE

$FEFF

 

$FEFC

$FEFD

$FEFC

$FEFD

 

 

 

 

 

 

 

 

 

 

 

 

1.If the high voltage (VDD + VHI) is removed from the IRQ1 pin or the RST pin, the SIM asserts its COP enable output. The COP is a mask option enabled or disabled by the COPD bit in the configuration register.

18.3.1.2 Normal Monitor Mode

Table 18-2shows the pin conditions for entering monitor mode.

MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1

256

Freescale Semiconductor

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Freescale Semiconductor MC68HC908MR32, MC68HC908MR16 manual Entering Monitor Mode, Mode Differences, Normal Monitor Mode
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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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