Q: Draw a flowchart for this programm.

GPIO_PORTF_DATA_R EQU 0x400253FC GPIO_PORTF_DIR_R EQU 0x40025400 GPIO_PORTF_AFSEL_R EQU 0x40025420 GPIO_PORTF_PUR_R EQU 0x40025510 GPIO_PORTF_DEN_R EQU 0x4002551C GPIO_PORTF_LOCK_R EQU 0x40025520 GPIO_PORTF_CR_R EQU 0x40025524 GPIO_PORTF_AMSEL_R EQU 0x40025528 GPIO_PORTF_PCTL_R EQU 0x4002552C GPIO_LOCK_KEY EQU 0x4C4F434B ; Unlocks the GPIO_CR register RED EQU 0x02 BLUE EQU 0x04 GREEN EQU 0x08 SW1 EQU 0x10 ; on the left side of the Launchpad board SW2 EQU 0x01 ; on the right side of the Launchpad board SYSCTL_RCGC2_R EQU 0x400FE108 SYSCTL_RCGC2_GPIOF EQU 0x00000020 ; port F Clock Gating Control

AREA |.text|, CODE, READONLY, ALIGN=2 THUMB EXPORT Start Start BL PortF_Init ; initialize input and output pins of Port F loop LDR R0, =FIFTHSEC ; R0 = FIFTHSEC (delay 0.2 second) BL delay ; delay at least (3*R0) cycles BL PortF_Input ; read all of the switches on Port F CMP R0, #0x01 ; R0 == 0x01? BEQ sw1pressed ; if so, switch 1 pressed CMP R0, #0x10 ; R0 == 0x10? BEQ sw2pressed ; if so, switch 2 pressed CMP R0, #0x00 ; R0 == 0x00? BEQ bothpressed ; if so, both switches pressed CMP R0, #0x11 ; R0 == 0x11? BEQ nopressed ; if so, neither switch pressed ; if none of the above, unexpected return value MOV R0, #(RED+GREEN+BLUE) ; R0 = (RED|GREEN|BLUE) (all LEDs on) BL PortF_Output ; turn all of the LEDs on B loop sw1pressed MOV R0, #BLUE ; R0 = BLUE (blue LED on) BL PortF_Output ; turn the blue LED on B loop sw2pressed MOV R0, #RED ; R0 = RED (red LED on) BL PortF_Output ; turn the red LED on B loop bothpressed MOV R0, #GREEN ; R0 = GREEN (green LED on) BL PortF_Output ; turn the green LED on B loop nopressed MOV R0, #0 ; R0 = 0 (no LEDs on) BL PortF_Output ; turn all of the LEDs off B loop

;------------delay------------ ; Delay function for testing, which delays about 3*count cycles. ; Input: R0 count ; Output: none ONESEC EQU 5333333 ; approximately 1s delay at ~16 MHz clock QUARTERSEC EQU 1333333 ; approximately 0.25s delay at ~16 MHz clock FIFTHSEC EQU 1066666 ; approximately 0.2s delay at ~16 MHz clock delay SUBS R0, R0, #1 ; R0 = R0 - 1 (count = count - 1) BNE delay ; if count (R0) != 0, skip to 'delay' BX LR ; return

;------------PortF_Init------------ ; Initialize GPIO Port F for negative logic switches on PF0 and ; PF4 as the Launchpad is wired. Weak internal pull-up ; resistors are enabled, and the NMI functionality on PF0 is ; disabled. Make the RGB LED's pins outputs. ; Input: none ; Output: none ; Modifies: R0, R1, R2 PortF_Init LDR R1, =SYSCTL_RCGC2_R ; 1) activate clock for Port F LDR R0, [R1] ORR R0, R0, #0x20 ; set bit 5 to turn on clock STR R0, [R1] NOP NOP ; allow time for clock to finish LDR R1, =GPIO_PORTF_LOCK_R ; 2) unlock the lock register LDR R0, =0x4C4F434B ; unlock GPIO Port F Commit Register STR R0, [R1] LDR R1, =GPIO_PORTF_CR_R ; enable commit for Port F MOV R0, #0xFF ; 1 means allow access STR R0, [R1] LDR R1, =GPIO_PORTF_AMSEL_R ; 3) disable analog functionality MOV R0, #0 ; 0 means analog is off STR R0, [R1] LDR R1, =GPIO_PORTF_PCTL_R ; 4) configure as GPIO MOV R0, #0x00000000 ; 0 means configure Port F as GPIO STR R0, [R1] LDR R1, =GPIO_PORTF_DIR_R ; 5) set direction register MOV R0,#0x0E ; PF0 and PF7-4 input, PF3-1 output STR R0, [R1] LDR R1, =GPIO_PORTF_AFSEL_R ; 6) regular port function MOV R0, #0 ; 0 means disable alternate function STR R0, [R1] LDR R1, =GPIO_PORTF_PUR_R ; pull-up resistors for PF4,PF0 MOV R0, #0x11 ; enable weak pull-up on PF0 and PF4 STR R0, [R1] LDR R1, =GPIO_PORTF_DEN_R ; 7) enable Port F digital port MOV R0, #0xFF ; 1 means enable digital I/O STR R0, [R1] BX LR

;------------PortF_Input------------ ; Read and return the status of the switches. ; Input: none ; Output: R0 0x01 if only Switch 1 is pressed ; R0 0x10 if only Switch 2 is pressed ; R0 0x00 if both switches are pressed ; R0 0x11 if no switches are pressed ; Modifies: R1 PortF_Input LDR R1, =GPIO_PORTF_DATA_R ; pointer to Port F data LDR R0, [R1] ; read all of Port F AND R0,R0,#0x11 ; just the input pins PF0 and PF4 BX LR ; return R0 with inputs

;------------PortF_Output------------ ; Set the output state of PF3-1. ; Input: R0 new state of PF ; Output: none ; Modifies: R1 PortF_Output LDR R1, =GPIO_PORTF_DATA_R ; pointer to Port F data STR R0, [R1] ; write to PF3-1 BX LR

ALIGN ; make sure the end of this section is aligned END ; end of file