<< Chapter < Page Chapter >> Page >

Storing data to memory

Storing the register contents uses the same addressing modes. The assembly instructions used for storing are STB , STH , and STW . Read and understand these instructions in the TI manual.

(Storing to memory): Write assembly instructions to store 32-bit constant 53fe 23e4h to memory address 0000 0123h .

Intentionally left blank.

Sometimes, it becomes necessary to access part of the data stored in memory. For example, if you store the 32-bit word 0x11223344 at memory location 0x8000 , the four bytes having addresses location 0x8000 , location 0x8001 , location 0x8002 , and location 0x8003 contain the value 0x11223344 . Then, if I read the byte data at memory location 0x8000 , what would be the byte value to be read?

The answer depends on the endian mode of the memory system. In the little endian mode , the lower memory addresses contain the LSB part of thedata. Thus, the bytes stored in the four byte addresses will be as shown in .

0x8000 0x44
0x8001 0x33
0x8002 0x22
0x8003 0x11

In the big endian mode , the lower memory addresses contain the MSB part of the data. Thus, we have

0x8000 0x11
0x8001 0x22
0x8002 0x33
0x8003 0x44

In this course, we use the little endian mode by default and all the lab programming must assume the little endian mode.

(Little endian mode): What will be the value in A0 after executing the following assembly instructions? (functional unit specificationswere omitted.)

  • MVKL 0x80000000, A10
  • MVKH 0x80000000, A10
  • MVKL 0x12345678, A9
  • MVKH 0x12345678, A9
  • STW A9, *A10
  • LDB *+A10[2],A0
What will be the value in A0 if the system uses the big endian mode?

Intentionally left blank.

In fact, the above addressing method describes the so-called linear addressing mode (default upon reset), where the offset or increment/decrement of pointers occurwithout bound. There is a circular addressing modes that can handle a finite size buffer efficiently. Youwill implement circular buffers for the FIR filtering algorithm in the FIR filtering experiments later.

In the C62x 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 is called 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

Questions & Answers

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.
yes that's correct
I think
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
scanning tunneling microscope
how nano science is used for hydrophobicity
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
what is differents between GO and RGO?
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
analytical skills graphene is prepared to kill any type viruses .
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
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
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
Privacy Information Security Software Version 1.1a
where are the solutions?
where are the solutions?

Get the best Algebra and trigonometry course in your pocket!

Source:  OpenStax, Finite impulse response. OpenStax CNX. Feb 16, 2004 Download for free at http://cnx.org/content/col10226/1.1
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Finite impulse response' conversation and receive update notifications?