BUS Arbitration Signals | Motorola MC68340 instruction

Freescale Semiconductor, Inc.

2.7.3 Data Strobe (DS)

DS is an output timing signal that applies to the data bus. For a read cycle, the MC68340 asserts DS and AS simultaneously to signal the external device to place data on the bus. For a write cycle, DS signals to the external device that the data to be written is valid. The MC68340 asserts DS approximately one clock cycle after the assertion of AS during a write cycle.

2.7.4 Transfer Size (SIZ1, SIZ0)

These output signals are driven by the bus master to indicate the number of operand bytes remaining to be transferred in the current bus cycle as noted in Table 2-4.

Table 2-4. SIZx Signal Encoding

SIZ1	SIZ0	Transfer Size
0	1	Byte
1	0	Word
1	1	Three Byte
0	0	Long Word

2.7.5 Read/Write (R/W)

This active-high output signal is driven by the bus master to indicate the direction of a data transfer on the bus. A logic one indicates a read from a slave device; a logic zero indicates a write to a slave device.

2.8 BUS ARBITRATION SIGNALS

The following signals are the bus arbitration control signals used to determine the bus master. Refer to Section 3 Bus Operation for more information on these signals.

2.8.1 Bus Request (BR)

This active-low input signal indicates that an external device needs to become the bus master.

2.8.2 Bus Grant (BG)

Assertion of this active-low output signal indicates that the MC68340 has relinquished the bus.

2.8.3 Bus Grant Acknowledge (BGACK)

Assertion of this active-low input indicates that an external device has become the bus master.

MOTOROLAMC68340 USER’S MANUAL2- 7

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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 BUS Arbitration Signals

Models: MC68340

Freescale Semiconductor, Inc.

Freescale Semiconductor, Inc.

2.7.3 Data Strobe (DS)

2.7.4 Transfer Size (SIZ1, SIZ0)

2.7.5 Read/Write (R/W)

2.8 BUS ARBITRATION SIGNALS

2.8.1 Bus Request (BR)

2.8.2 Bus Grant (BG)

2.8.3 Bus Grant Acknowledge (BGACK)

MC68340 specifications