#mecall test script

.text
.globl main

#You will update the relevant CSR registers to use your mecall subroutines when ecall is executed
#Program will try to (transfer control to a7? )unless ustatus ready bit is set to 1 (csrrsi zero, 0, 1)
#set vec table, enable interrupts to execute

main:
	li tp, 1 #set tp
	li t0, 0xfffffffc
	csrw t0, 64
	li t0, 0

	la t0, handler
 	csrrw zero, 5, t0 # set utvec (5) to the handlers address   #@  destination is 0, only changes source (t0) to csr# (5)
 	csrrsi zero, 0, 1 # set interrupt enable bit in ustatus (0)  #@ global interrupt enable, step 5?
 			  #set bit 0 to 1, of register 0


#INSTRUCTION_ADDR_MISALIGNED 	#0
#jump to an invalid address (like zero)
#try to load instruction at PC=0
li	t1, 3
jalr	t1

#INSTRUCTION_ACCESS_FAULT	#1
jalr zero

#LOAD_ADDRESS_MISALIGNED	#4
#ebreak
li	t1, 3
lw	t0, (t1)
#INSTR is stored in EPC but i lose it when printstr branches to teardown and overwrites it

#LOAD_ACCESS_FAULT		#5
ebreak
csrrsi zero, 0, 1 #WHY DO I NEED TO RESET USTATUS? what causes ustatus to be reset?
la	t1, main
lw	t0, 0(t1)

#STORE_ADDRESS_MISALIGNED	#6
csrrsi zero, 0, 1
li	t1, 3
sw	t0, 2(t1)

#STORE_ACCESS_FAULT		#7
csrrsi zero, 0, 1
la	t1, main
sw	t0, 0(t1)


#PART 1

	#get printstring working first to help with other routines
	#PrintString, #4
	la t0, mecall
	csrrw zero, 5, t0 # set utvec (5) to the handlers address
	csrrsi zero, 0, 1 # set interrupt enable bit in ustatus (0)
	li	a6, 4
	la	a0, startmsg
	ecall

ebreak
	jal PrintChar
	jal ReadChar
	jal ReadString
	#b	done	# once printstring works, move this line down by one.

done:
#Exit, #10
	li 	a6, 10
	#ecall		# remove this line to test mecall
	ecall
	li a7, 10
	ecall #Use normal ecall to exit

.data
startmsg:	.string "\nstarting mecall test"
promptstr:	.string	"\nType a string and press enter: "
promptint1:	.string	"\nType a single digit number and press enter: "
promptint2:	.string	"\nType '49' and press enter: "
promptchar:	.string	"\nenter a char: "
response:	.string	"\nYou entered: "
printcharmsg:	.string "\nLets print the letter 'a' : "
respint:	.word 0
respchar:	.byte '\0'
respstr:	.space 20


.text


ReadString: #8
#I CHANGED ALL USES OF A7 TO A6
	addi	sp, sp, -16
	sw 	ra, 12(sp)
	li 	a6, 4
	la 	a0, promptstr #This gets printed before we type a string. Need to loop until we reach enter key before doing this
	ecall
	li 	a6, 8
	la 	a0, respstr #Load a0 with 20 byte buffer (max len of str). This is where we store string
	ecall
	li 	a6, 4
	la 	a0, response
	ecall
	li 	a6, 4 #Call printstr
	la 	a0, respstr #Print respstr
	ecall
	lw 	ra, 12(sp)
	addi	sp, sp, 16
	ret

PrintChar: #11
	addi	sp, sp -16
	sw 	ra, 12(sp)
	li 	a6, 4
	la 	a0, printcharmsg
	ebreak
	ecall
	li 	a6, 11
	andi    t0, t0, 0
	addi 	a0, t0, 0x61 #hex 61 is letter a.
	ecall
	lw 	ra, 12(sp)
	addi	sp, sp, 16
	ret

ReadChar: #12
	addi	sp, sp, -16
	sw 	ra, 12(sp)
	li 	a6, 4
	la 	a0, promptchar
	ecall
	li 	a6, 12
	ecall
	addi 	t0, a0, 0
	li 	a6, 4
	la 	a0, response
	ecall
	li 	a6, 11
	addi 	a0, t0, 0
	ebreak
	ecall
	lw 	ra, 12(sp)
	addi	sp, sp, 16
	ret