; GPIO.s ; Runs on LM4F120 and TM4C123 ; Implements a NOT gate described in clas

Question

; GPIO.s

; Runs on LM4F120 and TM4C123

; Implements a NOT gate described in class

; PD3 is an output to LED, Positive logic

; PD0 is an input from switch, Positive logic

; Switch pressed causes LED to go OFF and

; release causes LED to go ON.

; **** To run this example in Simulator

; make sure and copy the C0DLL.dll file

;(in the folder where this [GPIO.s]file is)

; to your Keil ARM/Bin folder;

;;  Note that running the simulator gives 4 warnings

;;  Click OK and continue

GPIO_PORTD_DATA_R EQU 0x400073FC

GPIO_PORTD_DIR_R EQU 0x40007400

GPIO_PORTD_AFSEL_R EQU 0x40007420

GPIO_PORTD_DEN_R EQU 0x4000751C

SYSCTL_RCGCGPIO_R EQU 0x400FE608

AREA |.text|, CODE, READONLY, ALIGN=2

THUMB

EXPORT Start

GPIO_Init

; 1) activate clock for Port D

LDR R1, =SYSCTL_RCGCGPIO_R

LDR R0, [R1] ; R0 = [R1]

ORR R0, R0, #0x08 ; R0 = R0|0x08

STR R0, [R1] ; [R1] = R0

NOP

NOP

NOP

NOP ; allow time to finish activating

; 3) set direction register

LDR R1, =GPIO_PORTD_DIR_R ; R1 = &GPIO_PORTD_DIR_R

LDR R0, [R1] ; R0 = [R1]

ORR R0, R0, #0x08 ; R0 = R0|0x08 (make PD3 output)

;BIC R0, R0, #0x01 ; R0 = R0 & NOT(0x01) (make PD0 input)

STR R0, [R1] ; [R1] = R0

; 4) regular port function

LDR R1, =GPIO_PORTD_AFSEL_R ; R1 = &GPIO_PORTD_AFSEL_R

LDR R0, [R1] ; R0 = [R1]

BIC R0, R0, #0x09 ; R0 = R0&~0x09 (disable alt funct on PD3,PD0)

STR R0, [R1] ; [R1] = R0

; 5) enable digital port

LDR R1, =GPIO_PORTD_DEN_R ; R1 = &GPIO_PORTD_DEN_R

LDR R0, [R1] ; R0 = [R1]

ORR R0, R0, #0x09 ; R0 = R0|0x09 (enable digital I/O on PD3,PD0)

STR R0, [R1] ; [R1] = R0

BX LR

Start

BL GPIO_Init

LDR R0, =GPIO_PORTD_DATA_R

loop

LDR R1,[R0]

ORR R1, #0x08 ;

STR R1,[R0] ; Write to PortD DATA register to update LED on PD3

B loop ; unconditional branch to 'loop'

  ALIGN ; make sure the end of this section is aligned

  END ; end of file

how can i  Modify this sample code so Port D's pin 1, pin 3, and pin 5 output 3.3V. Also make Port D's pin 2 an input.

thank you

Explanation / Answer

To configure the Port pin as Output pin

1. Set corresponding port pin bit in Direction register (GPIO_PORTD_DIR_R)

2. Disable altenate function in GPIO_PORTD_AFSEL_R i.e clear corresponding port pin bit

3. Enable digital port in GPIO_PORTD_DEN_R i.e set corresponding port pin bit

To configure as input port pin

1. Clear corresponding port pin bit in Direction register (GPIO_PORTD_DIR_R)

2. Disable altenate function in GPIO_PORTD_AFSEL_R i.e clear corresponding port pin bit

3. Enable digital port in GPIO_PORTD_DEN_R i.e set corresponding port pin bit

Modified code:

PORTD PIN 1, 3 and 5 as output pin and generate logic high i.e. 3.3V

PORTD PIN 2 as input

; GPIO.s

; Runs on LM4F120 and TM4C123

; Implements a NOT gate described in class

; PD3 is an output to LED, Positive logic

; PD0 is an input from switch, Positive logic

; Switch pressed causes LED to go OFF and

; release causes LED to go ON.

; **** To run this example in Simulator

; make sure and copy the C0DLL.dll file

;(in the folder where this [GPIO.s]file is)

; to your Keil ARM/Bin folder;

;; Note that running the simulator gives 4 warnings

;; Click OK and continue

GPIO_PORTD_DATA_R EQU 0x400073FC

GPIO_PORTD_DIR_R EQU 0x40007400

GPIO_PORTD_AFSEL_R EQU 0x40007420

GPIO_PORTD_DEN_R EQU 0x4000751C

SYSCTL_RCGCGPIO_R EQU 0x400FE608

AREA |.text|, CODE, READONLY, ALIGN=2

THUMB

EXPORT Start

GPIO_Init

; 1) activate clock for Port D

LDR R1, =SYSCTL_RCGCGPIO_R

LDR R0, [R1] ; R0 = [R1]

ORR R0, R0, #0x08 ; R0 = R0|0x08

STR R0, [R1] ; [R1] = R0

NOP

NOP

NOP

NOP ; allow time to finish activating

;3) set direction register

LDR R1, =GPIO_PORTD_DIR_R ; R1 = &GPIO_PORTD_DIR_R

LDR R0, [R1] ; R0 = [R1]

ORR R0, R0, #0x2A ; R0 = R0|0x2A (make PD1 PD3 PD5 as output 101010 = 0x2A)

BIC R0, R0, #0x04 ; R0 = R0 & NOT(0x04) (make PD2 input 100 = 0x04)

STR R0, [R1] ; [R1] = R0

;4) regular port functions

LDR R1, =GPIO_PORTD_AFSEL_R ; R1 = &GPIO_PORTD_AFSEL_R

LDR R0, [R1] ; R0 = [R1]

BIC R0, R0, #0x2E ; R0 = R0&~0x2E (disable alt funct on PD1, PD3, PD5, PD2 101110 = 0x2E)

STR R0, [R1] ; [R1] = R0

;5) enable digital port

LDR R1, =GPIO_PORTD_DEN_R ; R1 = &GPIO_PORTD_DEN_R

LDR R0, [R1] ; R0 = [R1]

ORR R0, R0, #0x2E ; R0 = R0|0x2E (enable digital I/O on PD1, PD3, PD5, PD2)

STR R0, [R1] ; [R1] = R0

BX LR

Start

BL GPIO_Init

LDR R0, =GPIO_PORTD_DATA_R   

loop

LDR R1,[R0]

ORR R1, #0x2A ; Write Logic 1 to output 3.3V on PD1, PD3 and PD5

STR R1,[R0] ; Write to PortD DATA register to update LED on PD3

B loop ; unconditional branch to 'loop'

ALIGN ; make sure the end of this section is aligned

END ; end of file

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