Texas Instruments MSP50C6xx FIR FIR Filter Function Coefficients in RAM, An, *Rx 2nR+2, Rxeven++

Individual Instruction Descriptions

4.14.18 FIR

FIR Filter Function (Coefficients in RAM)

Syntax

[label]

name

dest, src

Clock, clk

Word, w

With RPT, clk

Class

FIR

An, *Rx

2

1

2(nR+2)

9a

Execution

With RPT N–2:

(mask interrupts)

RPT counter = N–2

MR = h[0] = first filter coefficient

x = sample data pointed at by Rxeven

h[1] = second filter coefficient pointed at Rxeven+1

y = result stored in three consecutive accumulators (32 bit) pointed by An

{between every accumulation}

IF TAG = 1

ELSE

Rxeven = Rxeven + R5

{for circular buffering}

ENDIF

Rxeven++

{ if Rx++ is specified in the instruction}

PC ⇐ PC + 1

{final result}

y +￿k+0..N–1

h[k] · x[N–1–k]

(Execution is detailed in section 4.11)

Flags Affected

None

Opcode

Instructions

16

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

FIR An, *Rx

1

1

1

0

1

0

0

An

0

1

0

Rx

1

1

Description

Finite impulse response (FIR) filter. Execute finite impulse response filter taps

using coefficients from data memory and samples from data memory. The

instruction specifies two registers, Rx and R(x+1) which sequentially address

coefficients and the sample buffer in the two instruction FIR tap sequence.

This instruction must be used with RPT instruction. When used with the repeat counter it will execute a 16 ⋅ 16 multiplication between two indirect addressed data memory buffers, 32-bit accumulation, and circular buffer operation. Executes in 2 instruction cycles.

Selected register Rx must be even. This instruction also uses R(x+1). See section 4.11 for more detail on the setup of coefficients and sample data. During FIR execution, interrupt is queued.

Assembly Language Instructions 4-101