SIM Counter | Freescale Semiconductor MC68HC908MR32, MC68HC908MR16

System Integration Module (SIM)

signal on the RST or the IRQ pin. This prevents the COP from becoming disabled as a result of external noise. During a break state, VHI on the RST pin disables the COP module.

14.3.2.3 Illegal Opcode Reset

The SIM decodes signals from the CPU to detect illegal instructions. An illegal instruction sets the ILOP bit in the SIM reset status register (SRSR) and causes a reset.

Because the MC68HC908MR32 has stop mode disabled, execution of the STOP instruction will cause an illegal opcode reset.

14.3.2.4 Illegal Address Reset

An opcode fetch from addresses other than FLASH or RAM addresses generates an illegal address reset (unimplemented locations within memory map). The SIM verifies that the CPU is fetching an opcode prior to asserting the ILAD bit in the SIM reset status register (SRSR) and resetting the MCU. A data fetch from an unmapped address does not generate a reset.

14.3.2.5 Forced Monitor Mode Entry Reset (MENRST)

The MENRST module monitors 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.

14.3.2.6 Low-Voltage Inhibit (LVI) Reset

The low-voltage inhibit (LVI) module asserts its output to the SIM when the VDD voltage falls to the VLVRX voltage and remains at or below that level for at least nine consecutive CPU cycles (see 19.5 DC Electrical

Characteristics). The LVI bit in the SIM reset status register (SRSR) is set, and the external reset pin (RST) is held low while the SIM counter counts out 4096 CGMXCLK cycles. Sixty-four CGMXCLK cycles later, the CPU is released from reset to allow the reset vector sequence to occur. The SIM actively pulls down the RST pin for all internal reset sources.

14.4 SIM Counter

The SIM counter is used by the power-on reset (POR) module to allow the oscillator time to stabilize before enabling the internal bus (IBUS) clocks. The SIM counter also serves as a prescaler for the computer operating properly (COP) module. The SIM counter overflow supplies the clock for the COP module. The SIM counter is 13 bits long and is clocked by the falling edge of CGMXCLK.

14.4.1 SIM Counter During Power-On Reset

The power-on reset (POR) module detects power applied to the MCU. At power-on, the POR circuit asserts the signal PORRST. Once the SIM is initialized, it enables the clock generation (CGM) module to drive the bus clock state machine.

14.4.2 SIM Counter and Reset States

External reset has no effect on the SIM counter. The SIM counter is free-running after all reset states. For counter control and internal reset recovery sequences, see 14.3.2 Active Resets from Internal Sources.

MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1

186	Freescale Semiconductor

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.

Freescale Semiconductor MC68HC908MR32, MC68HC908MR16 manual SIM Counter During Power-On Reset

Models: MC68HC908MR16 MC68HC908MR32