Parallel ROM Interface

8.7Attaching Additional Devices to the ROM Interface

The 21555 allows additional devices to be attached to the ROM interface. Two ROM interface signals are slightly redefined to support multiple devices by setting the Multiple Device Enable bit in the Chip Control 0 configuration register. In this mode, the maximum ROM size is reduced because the upper address lines are used to decode device select lines.

For this mode of operation, an external decoder is needed to decode the upper address bits into device select lines. The pr_ale_l signal is used to enable the device select decoder, in addition to enabling the clocking of the address registers. When pr_ale_l is low, the address registers are enabled, and when pr_ale_l is high, the device select decoder is enabled.

Note: Signal pr_ale_l must be driven low when the serial ROM is used to disable all other device select lines when an external decoder is used.

In addition, in this mode the pr_cs_l output pin is redefined to be a device ready input (pr_rdy). When pr_rdy is deasserted, the device select signal (controlled by pr_ale_l) and read or write strobe assertions are extended until pr_rdy is asserted again. The read and write strobes are deasserted upon detection of chip select deassertion (fall time for pr_ale_l) with the hold time specified by the strobe mask.

Note: When multiple devices are attached and multiple device mode is used, signal pr_cs_l should be pulled up through an external resistor.

Figure 18 illustrates how the interface is connected for use with multiple devices.

21555 Non-Transparent PCI-to-PCI Bridge User Manual

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Intel 21555 user manual Attaching Additional Devices to the ROM Interface
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21555 specifications

The Intel 21555 is a prominent microprocessor developed by Intel, designed to cater to a variety of computing needs. This processor marks a significant step forward in Intel's lineup and underscores the company's commitment to advancing technology in personal computing, enterprise solutions, and beyond.

One of the standout features of the Intel 21555 is its advanced architecture. It utilizes a multi-core design, enabling improved performance through parallel processing. This architecture allows multiple applications to run seamlessly without a decline in speed. The cores are built on a cutting-edge manufacturing process that enhances energy efficiency while maintaining high clock speeds.

The Intel 21555 supports a wide range of technologies, including Intel Turbo Boost, which enables dynamic adjustments to the processor’s performance based on workload demands. This feature allows the processor to accelerate its speed during intensive tasks, providing users with a responsive experience when it matters the most.

Another key characteristic of the Intel 21555 is its support for integrated graphics. With Intel UHD Graphics technology, users can enjoy enhanced visuals for everyday tasks such as video playback, web browsing, and light gaming. This eliminates the need for a separate graphics card for many users, particularly in home office or light gaming scenarios.

Security is a significant focus in the design of the Intel 21555. It includes built-in hardware-based security features like Intel Trusted Execution Technology and Secure Boot. These features help protect against various types of threats, ensuring that user data remains secure from malicious attacks.

The Intel 21555 is also optimized for use with Intel's platform technologies, including Intel Optane memory and Intel Rapid Storage Technology. These technologies work together to deliver faster boot times and improved system responsiveness, making computing more efficient for users.

Furthermore, the Intel 21555 is designed to support virtualization technologies, allowing multiple operating systems to run concurrently without compromising performance. This is particularly useful for developers and businesses that rely on virtualization for testing and development environments.

In summary, the Intel 21555 is a powerful and versatile processor that reflects Intel's ongoing innovation in the computing space. With its multi-core architecture, enhanced graphics capabilities, strong security features, and advanced technologies, it stands out as an excellent choice for a wide range of applications, serving both casual users and professionals alike.
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