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Port B Programming Examples

5.3.2 Sending Data on Port B

Example 5-2 shows how to configure Port B pins as outputs and use them for sending data.

Example 5-2. Sending Data on Port B

;*********************

;* OUTPUT example

*

;* for Port B

*

;* of DSP56824 chip *

;*********************

 

 

START

EQU

$0040

; Start of program

BCR

EQU

$FFF9

; Bus Control Register

PBD

EQU

$FFEC

; Port B Data

PBDDR

EQU

$FFEB

; Port B Data Direction Register

PBINT

EQU

$FFEA

; Port B Interrupt Register

data_o

EQU

$0001

; data output

;**************

 

 

 

;* Vector setup*

 

 

 

;**************

 

 

 

ORG

P:$0000

 

; Cold Boot

JMP

START

 

; also Hardware RESET vector (Mode 0, 1, 3)

ORG

P:$E000

 

; Warm Boot

JMP

START

 

; Hardware RESET vector (Mode 2)

ORG

P:START

 

; Start of program

;**************

 

 

 

;* General setup*

 

 

 

;**************

 

 

 

MOVEP

#$0000,X:BCR

; External Program memory has 0 wait states.

 

 

 

; External data memory has 0 wait states.

 

 

 

; Port A pins are tri-stated when no

;**************

 

 

; external access occurs.

 

 

 

;* Port B setup*

 

 

 

;**************

 

 

 

MOVEP

#$0000,X:PBINT

; Disable GPIO interrupt requests on

 

 

 

; all lower eight Port B pins (default).

MOVEP

#$FFFF,X:PBDDR

; Select pins PB0-PB15 as input (default).

;**************

 

 

 

;* Main routine*

 

 

 

;**************

 

 

;...

 

 

 

OUTPUT

 

 

; Output Loop

 

 

 

; ...

MOVE

X:data_o,X0

; Put bits 0-15 of “data_o” on pins PB0-PB15.

MOVEP

X0,X:PBD

; Memory to memory move requires two MOVEs.

BRA

OUTPUT

 

; ...

 

 

 

 

 

 

Port B GPIO Functionality

5-9

Соседние файлы в папке DSP568xx