Copctl Write | Freescale Semiconductor MC68HC908MR32, MC68HC908MR16

Computer Operating Properly (COP)

Addr.	Register Name
	COP Control Register	Read:
	COP Control Register
$FFFF	(COPCTL) Write:
	See page 77.	Reset:
		Reset:

Bit 7

Bit 0

Low byte of reset vector

Clear COP counter

Unaffected by reset

Figure 6-2. COP I/O Register Summary

The COP counter is a free-running, 6-bit counter preceded by the 13-bit system integration module (SIM) counter. If not cleared by software, the COP counter overflows and generates an asynchronous reset after 218–24CGMXCLK cycles. With a 4.9152-MHz crystal, the COP timeout period is 53.3 ms. Writing any value to location $FFFF before overflow occurs clears the COP counter and prevents reset.

A COP reset pulls the RST pin low for 32 CGMXCLK cycles and sets the COP bit in the SIM reset status register (SRSR). See 14.7.2 SIM Reset Status Register.

NOTE

Place COP clearing instructions in the main program and not in an interrupt subroutine. Such an interrupt subroutine could keep the COP from generating a reset even while the main program is not working properly.

6.3 I/O Signals

This section describes the signals shown in Figure 6-1.

6.3.1 CGMXCLK

CGMXCLK is the crystal oscillator output signal. CGMXCLK frequency is equal to the crystal frequency.

6.3.2 COPCTL Write

Writing any value to the COP control register (COPCTL) (see 6.4 COP Control Register) clears the COP counter and clears bits 12–4 of the SIM counter. Reading the COP control register returns the reset vector.

6.3.3 Power-On Reset

The power-on reset (POR) circuit in the SIM clears the SIM counter 4096 CGMXCLK cycles after power-up.

6.3.4 Internal Reset

An internal reset clears the SIM counter and the COP counter.

6.3.5 Reset Vector Fetch

A reset vector fetch occurs when the vector address appears on the data bus. A reset vector fetch clears the SIM counter.

MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1

76	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.

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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.

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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 Copctl Write, Power-On Reset, Internal Reset

Models: MC68HC908MR16 MC68HC908MR32