Chip Select Operation, Clock Control Signals

Freescale Semiconductor, Inc.

Table 4-2. System Frequencies from 32.768-kHz Reference

Y	W = 0; X = 0	W = 0; X = 1	W = 1; X = 0	W = 1; X = 1
000000	131	262	524	1049
000101	786	1573	3146	6291
001010	1442	2884	5767	11534
001111	2097	4194	8389	16777
010100	2753	5505	11010	22020
011001	3408	6816	13631	–
011111	4194	8389	16777	–
100011	4719	9437	18874	–
101000	5374	10748	21496	–
101101	6029	12059	24117	–
110010	6685	13369	–	–
110111	7340	14680	–	–
111100	7995	15991	–	–
111111	8389	16777	–	–

NOTE: System frequencies are in kHz.

4.2.3.3CLOCK CONTROL. The clock control circuits determine the source used for both internal and external clocks during special circumstances, such as low-power stop (LPSTOP) execution.

Table 4-3 summarizes the clock activity during LPSTOP in crystal mode operation. Any clock in the off state is held low. The STEXT and STSIM bits in the SYNCR control clock activity during LPSTOP. Refer to 4.2.6 Low-Power Stop for additional information.

Table 4-3. Clock Control Signals

Control Bits		Clock Outputs
STSIM	STEXT	SIMCLK	CLKOUT
0	0	EXTAL	Off
0	1	EXTAL	EXTAL
1	0	VCO	Off
1	1	VCO	VCO

NOTE: SIMCLK runs the periodic interrupt RESET and

IRQ≈ pin synchronizers in LPSTOP mode.

4.2.4 Chip Select Operation

Typical microprocessor systems require external hardware to provide select signals to external memory and peripherals. The MC68340 integrates these functions on chip to provide the cost, speed, and reliability benefits of a higher level of integration. The chip select function contains register pairs for each external chip select signal. The pair consists of a base address register and an address mask register that define the characteristics of a single chip select. The register pair provides flexibility for a wide variety of chip select functions.

MOTOROLAMC68340 USER’S MANUAL4- 13

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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 Chip Select Operation, System Frequencies from 32.768-kHz Reference

Models: MC68340

Freescale Semiconductor, Inc.

Freescale Semiconductor, Inc.

Table 4-2. System Frequencies from 32.768-kHz Reference

W = 0; X = 0

W = 1; X = 0

Table 4-3. Clock Control Signals

Control Bits

Clock Outputs

4.2.4 Chip Select Operation

MC68340 specifications