Honored Contributor
Honored Contributor.global alt_main
.text alt_main: movia sp, 0x00800000 //Set up stack address movia r10, 0x10000040 //Assigns r10 to address for slider switch movi r9, 0b00 //Used as initial contents of slider switch movi r11, 0b001 //Assigns value for SW0 movi r12, 0b010 //Assigns value for SW1 movi r13, 0b011 //Assigns value for SW2 movia r17, 0x00800030 //Assigns r17 to address for LCD control port movia r16, 0x00800040 //Assigns r18 to address for LCD data port call LCDportInit //Sets the port for the LCD to OUTPUT call LCDinit //Sets the details that the LCD will follow slider_check: ldbio r9, 0(r10) //Loads contents of the slider switch andi r9, r9, 0b011 //Checks only first 3 bits/switches beq r9, r0, slider_check //Loop if 0 beq r4, r9, slider_check //Loop is same as the check register r4 mov r4, r9 //Store new check register as equivalent to r9 beq r9, r11, Hello //If only first slider is on, branch to Hello beq r9, r12, HowAreYou //If only second slider is on, branch to HowAreYou beq r9, r13, IAmFine //If only third slider is on, branch to IAmFine Hello: movia r18, Message1 //Assigns r18 as the address of Message1 call LCDprintString //Run the subroutine to print the message br slider_check HowAreYou: movia r18, Message2 //Assigns r18 as the address of Message2 call LCDprintString //Run the subroutine to print the message br slider_check IAmFine: movia r18, Message3 //Assigns r18 as the address of Message3 call LCDprintString //Run the subroutine to print the message br slider_check LCDcmdWrt: subi sp, sp, 8 //Make room on stack stw r6, 0(sp) //Save r6 stw ra, 4(sp) //Save ra incase another //subroutine is called call delay_20ms //Time needed to perform command movi r6, 0 //E=RS=RW=0 stbio r6, 0(r17) //LCD control port stbio r7, 0(r16) //Send command to LCD data port. The command //is passed to subroutine in r7 ori r6, r6, 0b100 //E = 1 stbio r6, 0(r17) //LCD control port call delay_500ns //Keep E high > 450ns andi r6, r6, 0b11111011 //E = 0 stbio r6, 0(r17) //LCD control port ldw r6, 0(sp) //restore r6 ldw ra, 4(sp) //restore ra addi sp, sp, 8 //restore sp up to initial address ret LCDdataWrt: subi sp, sp, 8 //Make room on stack stw r6, 0(sp) //Save r6 stw ra, 4(sp) //Save ra incase another subroutine is called call delay_20ms //Time needed to perform command movi r6, 0b010 //E=0 RS=1 RW=0 stbio r6, 0(r17) //LCD control port stbio r7, 0(r16) //Send command to LCD data port. The command //is passed to subroutine in r7 ori r6, r6, 0b100 //E = 1 stbio r6, 0(r17) //LCD control port call delay_500ns //Keep E high > 450ns andi r6, r6, 0b11111011 //E = 0 stbio r6, 0(r17) //LCD control port ldw r6, 0(sp) //restore r6 ldw ra, 4(sp) //restore ra addi sp, sp, 8 //restore sp up to initial address ret LCDportInit: subi sp, sp, 8 //Make room on stack stw r6, 0(sp) //Save r6 stw ra, 4(sp) //Save ra incase another subroutine is called movi r6, 0xff //Value used to initiate the LCD as OUTPUT stbio r6, 4(r17) //Store to LCD control port stbio r6, 4(r16) //Store to LCD data port ldw r6, 0(sp) //restore r6 ldw ra, 4(sp) //restore ra addi sp, sp, 8 //restore sp up to initial address ret LCDinit: subi sp, sp, 4 //Make room on stack stw ra, 0(sp) //Save ra movi r7, 0x38 //Data length 8-bits, 5x7 font call LCDcmdWrt movi r7, 0x0f //display ON, cursor ON, cursor Blink call LCDcmdWrt movi r7, 0x01 //clear display call LCDcmdWrt movi r7, 0x06 //increment cursor position call LCDcmdWrt movi r7, 0x02 //home cursor call LCDcmdWrt ldw ra, 0(sp) //restore ra addi sp, sp, 4 //restore sp up to initial address ret LCDprintString: subi sp, sp, 8 //Make room on stack stw r7, 0(sp) //Save r7 stw ra, 4(sp) //Save ra movi r7, 0x01 //clear display call LCDcmdWrt movi r7, 0x02 //home cursor call LCDcmdWrt next_char: ldb r7, 0(r18) //Load the current character in the string beq r7, r0, end_printString //If LCD has reached the '0' at the end //of the string, go to end_printString call LCDdataWrt //Run the subroutine LCDdataWrt addi r18, r18, 0x01 //Add 1 to the character string value br next_char //Loop the current subroutine end_printString: ldw r7, 0(sp) //Restore r7 ldw ra, 4(sp) //Restore ra addi sp, sp, 8 //Restore sp up to initial address ret delay_20ms: subi sp, sp, 8 //Allocate 8 bytes on stack stw r6, 0(sp) //Save r6 stw ra, 4(sp) //Save return address, allows nesting subroutines movia r6, 45455 //This value allows for 20ms to pass again_20ms: subi r6, r6, 1 bne r6, r0, again_20ms ldw r6, 0(sp) //Restore r6 ldw ra, 4(sp) //Restore return address addi sp, sp, 8 //de-allocate stack locations ret delay_500ns: andi r0, r0, 0b0 //These instructions will provide enough andi r0, r0, 0b0 //time to complete the necessary delay time ret .data Message1: .asciz "Hello" Message2: .asciz "How are you?" Message3: .asciz "I am fine" .end
