Read-Modify-Write Cycle | Motorola MC68340 specs

Freescale Semiconductor, Inc...

Freescale Semiconductor, Inc.

State 4—The MC68340 issues no new control signals during S4.

State 5—The MC68340 negates AS and DS during S5. It holds the address and data valid during S5 to provide address hold time for memory systems. R/ W, SIZ1/SIZ0, and FC3– FC0 also remain valid throughout S5. The external device must keep DSACK≈ asserted until it detects the negation of AS or DS (whichever it detects first). The device must negate DSACK≈ within approximately one clock period after sensing the negation of AS or DS. DSACK≈ signals that remain asserted beyond this limit may be prematurely detected for the next bus cycle.

3.3.3 Read-Modify-Write Cycle

The read-modify-write cycle performs a read, conditionally modifies the data in the arithmetic logic unit, and may write the data out to memory. In the MC68340, this operation is indivisible, providing semaphore capabilities for multiprocessor systems. During the entire read-modify-write sequence, the MC68340 asserts RMC to indicate that an indivisible operation is occurring. The MC68340 does not issue a BG signal in response to a BR signal during this operation. Figure 3-9 is an example of a functional timing diagram of a read-modify-write instruction specified in terms of clock periods.

S0	S2	S4	S0	S2	S4	S0
CLK OUT
A31–A30
FC3–FC0
SIZ1–SIZ0
R/W
RMC
AS
DS
DSACKx
D15–D0
	READ			WRITE
			INDIVISIBLE
			CYCLE

Figure 3-9. Read-Modify-Write Cycle Timing

MOTOROLA

MC68340 USER’S MANUAL

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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 Read-Modify-Write Cycle Timing

Models: MC68340