Pulse-Width Measurement | Motorola MC68340 instruction

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immediately after the SWR and CPE bits in the CR are set. The SR TG bit cannot be set. At all times, the TGL bit in the SR reflects the level of TGATE≈.

The width of the pulse generated on TOUTx (the value in PREL2) can be changed while the counter is counting down from the value in PREL1. Caution must be used because, if PREL2 is accessed simultaneously by the counting logic and a CPU32 write, the old PREL2 value may actually get loaded into the counter at timeout.

8.3.5 Pulse-Width Measurement

This mode is used to count the clock cycles during a particular event (see Figure 8-8). The event is defined by the assertion and negation of TGATE≈. When TGATE≈ is asserted, the counter begins counting down from $FFFF. When TGATE≈ is negated, the counter stops counting and holds the value at which it stopped. Further assertions and negations of TGATE≈ have no effect on the counter. This mode can be selected by programming the CR MODEx bits to 100.

The timer is enabled by setting the SWR, CPE, and TGE bits in the CR. Asserting TGATE≈ starts the counter. When the timer is enabled, the SR ON bit is set. On the next falling edge of the counter clock, the counter is loaded with the value $FFFF. With each successive falling edge of the counter clock, the counter decrements. The PREL1 and PREL2 registers are not used in this mode.

When TGATE≈ is negated, the SR TG bit is set, the ON bit is negated, and the prescaler and counter are disabled. Subsequent transitions on TGATE≈ do not re-enable the counter. The TGL bit in the SR reflects the level of TGATE≈ at all times.

COUNTER
CLOCK
COUNTER 0	f	f	f	f		f	f
	f	f	f	f		f	f
	f	f	f	f		f	f
	f	e	d	c		b	b
TGATE		MEASURED PULSE
		MEASURED PULSE
ENABLE
	START				STOP		NO EFFECT
	COUNTING				COUNTING

MODEx Bits in Control Register = 100

TGE Bit of Control Register = 1

Figure 8-8. Pulse-Width Measurement Mode

If the counter counts down to the value stored in the COM register, the COM and TC bits in the SR are set. If the counter counts down to $0000, a timeout is detected. This sets the SR TO, and the clears the COM bit. At timeout, the next falling edge of the counter clock

8- 12MC68340 USER’S MANUALMOTOROLA

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MC68340 specifications

The Motorola MC68340 is a highly integrated microprocessor that was introduced in the early 1990s. It belongs to the 68000 family of microprocessors and is designed to cater to the demands of embedded systems, particularly in telecommunications and networking applications. This chip represents a significant evolution in microprocessor technology by combining a microprocessor core with additional peripherals on a single chip, making it an attractive solution for engineers looking to design compact and efficient systems.

One of the key features of the MC68340 is its 32-bit architecture, which allows for significant processing power and data handling capabilities. This architecture enables the processor to handle larger data sizes and perform more complex calculations compared to its 16-bit predecessors. The MC68340 operates at clock speeds typically ranging from 16 MHz to 25 MHz. Its dual instruction pipeline enhances throughput, allowing for simultaneous instruction fetches and executions, which significantly boosts performance.

A notable characteristic of the MC68340 is the inclusion of integrated peripherals, which help reduce the overall component count in a system. Key integrated components include a memory management unit (MMU), a direct memory access (DMA) controller, and various communication interfaces such as serial ports. The memory management capabilities enhance the processor's ability to manage memory resources efficiently, enabling it to support multitasking environments commonly found in modern computing.

In terms of connectivity, the MC68340 features connections for both synchronous and asynchronous serial communication, making it well-suited for networking tasks. The processor supports a range of bus standards, including address and data buses, which facilitate seamless interaction with peripheral devices.

Another important aspect of the MC68340 is its flexibility. The processor supports multiple operating modes, including multiple CPU configurations and compatibility with the Motorola 68000 family, allowing for easier integration into existing systems.

Moreover, the MC68340 boasts low power consumption compared to many of its contemporaries, making it an excellent choice for battery-operated applications, enhancing its appeal in sectors like telecommunications, industrial control, and automotive systems. Its combination of performance, integration, versatility, and efficiency has secured the MC68340 a reputable position in the annals of embedded systems technology, proving to be a valuable asset for developers and engineers alike.

Motorola MC68340 manual Pulse-Width Measurement Mode

Models: MC68340

Freescale Semiconductor, Inc.

Freescale Semiconductor, Inc.

8.3.5 Pulse-Width Measurement

Figure 8-8. Pulse-Width Measurement Mode

MC68340 specifications