Monitor ROM (MON)

Enter monitor mode by either:

•Executing a software interrupt instruction (SWI) or

•Applying a logic 0 and then a logic 1 to the RST pin

Once out of reset, the MCU waits for the host to send eight security bytes. After receiving the security bytes, the MCU sends a break signal (10 consecutive logic 0s) to the host computer, indicating that it is ready to receive a command. The break signal also provides a timing reference to allow the host to determine the necessary baud rate.

Monitor mode uses alternate vectors for reset and SWI. The alternate vectors are in the $FE page instead of the $FF page and allow code execution from the internal monitor firmware instead of user code. The computer operating properly (COP) module is disabled in monitor mode as long as VHI is applied to either

the IRQ pin or the RST pin. (See Chapter 14 System Integration Module (SIM) for more information on modes of operation.)

18.3.1.3 Forced Monitor Mode

If the voltage applied to the IRQ1 is less than VDD + VHI the MCU will come out of reset in user mode. The MENRST module is monitoring the reset vector fetches and will assert an internal reset if it detects that the reset vectors are erased ($FF). When the MCU comes out of reset, it is forced into monitor mode without requiring high voltage on the IRQ1 pin.

The COP module is disabled in forced monitor mode. Any reset other than a POR reset will automatically force the MCU to come back to the forced monitor mode.

18.3.1.4 Data Format

Communication with the monitor ROM is in standard non-return-to-zero (NRZ) mark/space data format. (See Figure 18-9and Figure 18-10.)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

NEXT

START

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

START

 

BIT 0

 

BIT 1

 

BIT 2

 

BIT 3

 

BIT 4

 

BIT 5

 

BIT 6

 

BIT 7 STOP

BIT

 

 

 

 

 

 

 

 

 

BIT

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

BIT

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

START

$A5 BIT

START

BREAK BIT

Figure 18-9. Monitor Data Format

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

NEXT

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

START

BIT 0

 

BIT 1

 

BIT 2

 

BIT 3

BIT 4

 

BIT 5

 

BIT 6

 

BIT 7

STOP

 

 

 

 

 

 

 

BIT

 

 

 

 

 

 

 

 

 

 

 

 

 

 

BIT

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

STOP

 

 

BIT 0

 

BIT 1

 

BIT 2

 

BIT 3

BIT 4

 

BIT 5

 

BIT 6

 

BIT 7

 

NEXT

 

 

 

 

 

 

BIT

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

START

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

BIT

Figure 18-10. Sample Monitor Waveforms

The data transmit and receive rate can be anywhere from 4800 baud to 28.8 Kbaud. Transmit and receive baud rates must be identical.

MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1

Freescale Semiconductor

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Freescale Semiconductor MC68HC908MR16, MC68HC908MR32 manual Forced Monitor Mode, Data Format
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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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