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

Techno hype - obstacle to information system, Techno hype - Obstacle to Inf...

Techno hype - Obstacle to Information System New technology has always been accompanied by a certain amount of euphoria that inevitably leads to unrealistic expectations place

Why we need linker, Q. Why we need linker?  The linker: Joins as...

Q. Why we need linker?  The linker: Joins assembled module in one executable program, Produces an .EXE module and initializes with special instructions to facilitate

Slope deflection equations, Slope Deflection Equations for a Member: I...

Slope Deflection Equations for a Member: In this section, we will develop a few general equations needed for further discussion in the moment distribution context. Fig

Fundamental issues of concerns for instruction set design, Q. Fundamental i...

Q. Fundamental issues of concerns for instruction set design? A number of fundamental issues of concerns for instruction set design are: Completeness: For an early design

Significance of having less memory references, Q. What is the significance ...

Q. What is the significance of having less memory references? As the time needed for memory reference is more than that of a register reference so increased number of memory r

Is it possible to decrease clock skew to zero, Is it possible to decrease c...

Is it possible to decrease clock skew to zero? Describe your answer? Even if there are clock layout strategies (H-tree) which can into theory reduce clock skew to zero by havi

Explain the structure of virtual enterprise, Explain the Structure of Virtu...

Explain the Structure of Virtual Enterprise. The virtual enterprise can be a suitable structure to explore the emerging opportunities for forming value in the information socie

Displaying a number, Displaying a number Supposing that two digit num...

Displaying a number Supposing that two digit number 59 is stored as number 5 in BH and number 9 in BL to convert them to equivalent ASCII we will add "0" to each one of them.

Work systems framework - information system, The Work Systems Framework - I...

The Work Systems Framework - Information System Adler writing in 1992 used the phrase 'stumbling backwards into the future' to describe the neglect organisations at that time

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