Interrupt and Scratchpad Registers

11.3Doorbell Interrupts

A 16-bit software controlled interrupt request register and an associated 16-bit mask register is implemented for each interface (primary and secondary). Each register is byte addressable for use as two sets of 8-bit interrupt request and interrupt mask registers for each interface (four in all) if desired. These registers can be accessed from the primary or secondary interface of the 21555, in either memory space or I/O space.

The 21555 doorbell interrupt functionality consists of the following registers:

•Primary Interrupt Request 16-bit register.

•Secondary Interrupt Request 16-bit register.

•Primary Interrupt Request (IRQ) Mask 16-bit register.

•Secondary Interrupt Request (IRQ) Mask 16-bit register.

The primary interrupt pin, p_inta_l, is asserted low whenever one or more Primary Interrupt Request bits are set and their corresponding Primary IRQ Mask bits are 0. Signal p_inta_l remains asserted as long as this condition exists. Signal p_inta_l is deasserted when either the Primary Interrupt Request bit is cleared or the Primary IRQ Mask bit is set. The secondary interrupt pin, s_inta_l, is asserted low when one or more Secondary Interrupt Request bits are set and their corresponding Secondary IRQ Mask bits are 0 (zero), and remains asserted as long as this condition exists. The signal s_inta_l is deasserted when either the Secondary Interrupt Request bit is cleared or the Secondary IRQ Mask bit is set.

Each register can be accessed at two addresses. One location is used to set bits and the other location is used to clear them. To modify a request bit, a 1 is written to the bit in either the

write-1-to-set interrupt or write-1-to-clear interrupt register address. Interrupt status can be read from either register.

11.4Scratchpad Registers

Table 106, “Scratchpad 0 Through Scratchpad 7 Registers” on page 174 lists the bit descriptions of the scratchpad 0 through scratchpad 7 registers.

The eight 32-bit scratchpad registers can be accessed in either memory or I/O space from either the primary or secondary interface. They can pass control and status information between primary and secondary bus devices or they can be generic R/W registers.

Writing or reading a scratchpad register does not cause an interrupt to be asserted. Doorbell interrupts can be used for this purpose.They are read/write scratchpad registers.

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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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