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Then, why didn't the designer of the CPU make such that LDW instruction takes 5 clock cycles to begin with, rather than let the programmer insert 4 NOPs ? The answer is that you can insert other instructions other than NOPs as far as those instructions do not use the result of the LDW instruction above. By doing this, the CPU can execute additional instructions while waiting for the result of the LDW instruction to be valid, greatly reducing the total execution time of the entire program.

Delay slots

In the C6x CPU, it takes exactly one CPU clock cycle to execute each instruction. However, the instructions such as LDW need to access the slow external memory and the results of the load are not availableimmediately at the end of the execution. This delay of the execution results iscalled delay slots .

For example, let's consider loading up the content of memory content at address pointed by A10 to A1 and then moving the loaded data to A2 . You might be tempted to write simple 2 line assembly codeas follows:

1 LDW .D1 *A10, A1 2 MV .D1 A1,A2

What is wrong with the above code? The result of the LDW instruction is not available immediately after LDW is executed. As a consequence, the MV instruction does not copy the desired value of A1 to A2 . To prevent this undesirable execution, we need to make the CPU wait until the resultof the LDW instruction is correctly loaded to A1 before executing the MV instruction. For load instructions, we need extra 4 clock cycles until the loadresults are valid. To make the CPU wait for 4 clock cycles, we need to insert 4 NOP (no operations) instructions between LDW and MV . Each NOP instruction makes the CPU idle for one clock cycle. The resulting code will be likethis:

1 LDW .D1 *A10, A1 2 NOP3 NOP 4 NOP5 NOP 6 MV .D1 A1,A2

or simply you can write

1 LDW .D1 *A10, A1 2 NOP 43 MV .D1 A1,A2

Why didn't the designer of the CPU make such that LDW instruction takes 5 clock cycles to begin with, rather than let the programmer insert 4 NOPs ? The answer is that you can insert other instructions other than NOPs as far as those instructions do not use the result of the LDW instruction above. By doing this, the CPU can execute additional instructions while waiting for the result of the LDW instruction to be valid, greatly reducing the total execution time of the entire program.

Delay slots
Description Instructions Delay slots
Single Cycle All instructions except following 0
Multiply MPY, SMPY etc. 1
Load LDB, LDH, LDW 4
Branch B 5

The functional unit latency indicates how many clock cycles each instruction actually uses afunctional unit. All C6x instructions have 1 functional unit latency, meaning that each functional unit is ready toexecute the next instruction after 1 clock cycle regardless of the delay slots of the instructions. Therefore, thefollowing instructions are valid:

1 LDW .D1 *A10, A4 2 ADD .D1 A1,A2,A3

Questions & Answers

where we get a research paper on Nano chemistry....?
Maira Reply
what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
learn
Google
da
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Bhagvanji
hey
Giriraj
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
revolt
da
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
Nasa has use it in the 60's, copper as water purification in the moon travel.
Alexandre
nanocopper obvius
Alexandre
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
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Source:  OpenStax, Dsp lab with ti c6x dsp and c6713 dsk. OpenStax CNX. Feb 18, 2013 Download for free at http://cnx.org/content/col11264/1.6
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