# Connexions

You are here: Home » Content » FIR Filtering: Basic Assembly Exercise for TI TMS320C54x

### Recently Viewed

This feature requires Javascript to be enabled.

### Tags

(What is a tag?)

These tags come from the endorsement, affiliation, and other lenses that include this content.

# FIR Filtering: Basic Assembly Exercise for TI TMS320C54x

Summary: You will work through a section of TI TMS320C54x assembly code by hand. The instructions include multiplication of fractional numbers in two's complement representation.

Note: You are viewing an old version of this document. The latest version is available here.

## Assembly Exercise

Analyze the following lines of code. Refer to Two's Complement and Fractional Arithmetic for 16-bit Processors, Addressing Modes for TI TMS320C54x, and the Mnemonic Instruction Set [link] manual for help.



1  FIR_len .set    3
2
3  ; Assume:
4  ;   BK = 3
5  ;   AR0 = 1
6  ;   AR2 = 1000h
7  ;   AR3 = 1004h
8  ;
9  ;   FRCT = 1
10
11      stl     A,*AR3+%
12      rptz    A,(FIR_len-1)
13      mac     *AR2+0%,*AR3+0%,A



Anything following a ";" is considered a comment. In this case, the comments indicate the contents of the auxiliary registers, BK, AR0, AR2, and AR3 before the execution of the first instruction, stl. Note that any number followed by an "h" or preceded with a 0x represents a hexadecimal value.

### Example 1

1000h and 0x1000 both refer to the decimal number 4096.

Assume that the data memory is initialized as follows starting at location 1000h.

After familiarizing yourself with the stl, rptz, and mac instructions, step through each line of code and record the values of the accumulator A and auxiliary registers AR2 and AR3 in the spaces provided in Figure 2. Additionally, record the value of the memory contents after all three instructions have been "executed" in the blank data memory table provided in Figure 3.

Figure 2: Execution Results
A AR2 AR3
00 0000 8000h 1000h 1004h at start of code
after stl instruction
after rptz instruction
after first mac instruction
after second mac instruction
after third mac instruction

When working through the exercise, take into account that the accumulator A is a 40-bit register, and that the multiplier is in the fractional arithmetic mode. In this mode, integers on the DSP are interpreted as fractions, and the multiplier will treat them accordingly. This is done by shifting the result of the integer multiplier in the ALU left one bit. (Assume the multiplier is in fractional arithmetic mode for all exercises, unless you are told otherwise.) Therefore, multiplies performed by the ALU (via the mac instruction) produce a result that is twice what you would expect if you just multiplied the two integers together. DSP numerical representation and arithmetic are described further in Two's Complement and Fractional Arithmetic for 16-bit Processors.

## Content actions

### Give feedback:

My Favorites (?)

'My Favorites' is a special kind of lens which you can use to bookmark modules and collections. 'My Favorites' can only be seen by you, and collections saved in 'My Favorites' can remember the last module you were on. You need an account to use 'My Favorites'.

| A lens I own (?)

#### Definition of a lens

##### Lenses

A lens is a custom view of the content in the repository. You can think of it as a fancy kind of list that will let you see content through the eyes of organizations and people you trust.

##### What is in a lens?

Lens makers point to materials (modules and collections), creating a guide that includes their own comments and descriptive tags about the content.

##### Who can create a lens?

Any individual member, a community, or a respected organization.

##### What are tags?

Tags are descriptors added by lens makers to help label content, attaching a vocabulary that is meaningful in the context of the lens.

| External bookmarks