Freescale Semiconductor, Inc...

Freescale Semiconductor, Inc.

FCM3–FCM0—Function Code Mask Bits 3–0

This field can be used to mask certain function code bits, allowing more than one address space type to be assigned to a chip select. Any set bit masks the corresponding function code bit.

DD1, DD0—DSACK Delay Bits 1 and 0

This field determines the number of wait states added before an internal DSACK≈ is returned for that entry. Table 4-10 lists the encoding for the DD bits.

NOTE:

The port size field must be programmed for an internal DSACK≈ response and the FTE bit in the base address register must be cleared for the DDx bits to have significance. If external DSACK≈ signals are returned earlier than indicated by the DDx bits, the cycle will terminate sooner than programmed. See 4.2.5.2 PORT B for a discussion on using the internal DSACK≈ generation without using the CS≈ signal.

Table 4-10. DDx Encoding

DD1

DD0

Response

0

0

Zero Wait State

0

1

One Wait State

1

0

Two Wait States

1

1

Three Wait States

PS1, PS0—Port Size Bits 1 and 0

This field determines whether a given chip select responds with DSACK≈ and, if so, what port size is returned. Table 4-11 lists the encoding for the PSx bits.

Table 4-11. PSx Encoding

PS1

PS0

Mode

0

0

Reserved*

0

1

16-Bit Port

1

0

8-Bit Port

1

1

External DSACK≈ Response

*Use only for 32-bit DMA transfers.

To use the external DSACK≈ response, PS1–PS0 = 11 should be selected to suppress internal DSACK≈ generation. The DDx bits then have no significance.

4- 32MC68340 USER’S MANUALMOTOROLA

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Motorola MC68340 manual DDx Encoding, PSx Encoding, Response, Mode
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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.
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