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

What are the requirements a dialog program must fulfill, What are the requi...

What are the requirements a dialog program must fulfill? A dialog program must fulfil the following requirements A user friendly user interface. - Format and consistency

Explain priority interrupt, What is priority interrupt? A priority inte...

What is priority interrupt? A priority interrupt is an interrupt that establishes a priority over the various sources to verify which condition is to be serviced first when two

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

Define physical context, Question : Context aware mobile web applicatio...

Question : Context aware mobile web applications are the important to achieve ubiquity, device independence and personalization. The context provides detailed information about

What are the types of assemblies, What are the Types of Assemblies? One...

What are the Types of Assemblies? One of the drawback of using Visual Studio.NET and the .NET framework to develop applications has been the lack of cross-platform support. As

What do you mean by digital computer, COMPUTER ORGANIZATION & ARCHITECTURE ...

COMPUTER ORGANIZATION & ARCHITECTURE 1. What do you mean by digital computer? Explain the block diagram of a digital computer. 2. What do you mean by Difference Engine? Expl

How can we write an interrupt servicing routine, Q. How can we write an Int...

Q. How can we write an Interrupt Servicing Routine? The following are the fundamentalthough rigid sequence of steps: 1.  Save the system context (flags,registers etc. which

Describe loading disk operating system, Q. Describe Loading Disk Operating ...

Q. Describe Loading Disk Operating System? Different version of DOS, such as 2.0, 3.0, 3.2, 4.0, 5.0, 6.0, 6.2, 6.22, 7.0, 7.2 are present. The newer versions have additional

What is the difference among thread and process, Thread is a least unit of ...

Thread is a least unit of process. In process have one or more thread.

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