Address phase - computer architecture, Computer Engineering

Assignment Help:

Address phase:

A PCI bus transaction starts having an address phase. The initiator,  after seeing that it has GNT# and the bus is inactive, drives the target address onto the AD[31:0] lines, the associated command (for example: I/O write or memory read,) on the C/BE[3:0]# lines, and pulls FRAME# low.

Each other device inspect the address and command & decides whether to respond as the target by asserting DEVSEL#. Device has to respond by asserting DEVSEL# within 3 cycles. Devices which promise to respond within one or two cycles are said to have "fast DEVSEL" or "medium DEVSEL", respectively. (In fact, the time to respond is 2.5 cycles, since PCI devices have to transmit all signals half a cycle early so that they can be retaining3 cycles later.)Note that a device have to latch the address on the first cycle; the initiator is needed to remove the address and command from the bus on the following cycle, even before retaining a DEVSEL# response. The extra time is available only for interpreting the address and command after it is captured. On the fifth cycle of the address phase (or earlier if all other devices have medium DEVSEL or faster), a catch-all "subtractive decoding" is permitted for some address ranges. It is generally used by an ISA bus bridge for addresses within its particular range (16 bits for I/O and 24 bits for memory).

On the sixth cycle, if there has been no response, the initiator can abort the transaction by deserting FRAME#. It is known as master abort termination and it is customary for PCI bus bridges to return all- ones data (0xFFFFFFFF) in this particular case. PCI devices therefore are generally designed to ignore by using the all-ones value in essential status registers, so that such type of error may be easily detected by software.

 


Related Discussions:- Address phase - computer architecture

Explain about RISC architecture, Q. Explain about RISC ARCHITECTURE? Le...

Q. Explain about RISC ARCHITECTURE? Let's first list some significant considerations of RISC architecture: 1. RISC functions are kept simple unless there is a very good reas

What is directory, What is Directory?   The device directory or simply ...

What is Directory?   The device directory or simply called as directory records information-such as name, location, size, and type for all files on that certain partition. The

Explain the e-cheques verses credit cards in brief, Explain the E-cheques v...

Explain the E-cheques verses Credit Cards in brief. E-cheques: E-cheques are utilized for business dealing into e-commerce. Transactions of such cheques take place onto Inter

How to copy files from a drive and directory, Q. How to copy files from a d...

Q. How to copy files from a drive and directory? You can copy files from a drive and directory other that the currently selected one. However in that case, you need to speci

How is basic authentication worked, How is basic authentication worked? ...

How is basic authentication worked? When an exact resource has been protected using fundamental authentication, Apache sends a 401 Authentication needed header along with the r

Data routing functions-network properties, Data Routing Functions The d...

Data Routing Functions The data routing functions are the functions which when implemented  the path among the source and the objective. In dynamic interconnection networks the

What is a heap, What is a heap? A complete binary tree, every of whose ...

What is a heap? A complete binary tree, every of whose elements contains a value that is  greater than or equal to the value of every of its children is known a Heap

Describe ergonomic keyboards, Q. Describe Ergonomic Keyboards? Ergonomi...

Q. Describe Ergonomic Keyboards? Ergonomics is the study of environment, conditions as well as efficiency of workers. Ergonomics proposes that keyboard wasn't designed with hum

What is the difference between strong ai and weak ai, Strong AI makes the b...

Strong AI makes the bold claim that computers can be made to think on a level (at least) equivalent to humans. Weak AI only states that some "thinking-like" features can be added t

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd