the In lecture I will discuss how to write the basic main loop for an embedded controller. Based
on the TV.asm given in the lecture downloadable from the slides, write a process_input function
that responds to `m, `h, `q (ascii code 109, 104, 112, respectively).
The TV is initially not in the ``menu state. When the user presses `m while the TV is not in the
menu state, the TV should show as very simple menu, and enters the menu state (recall your
own TV for reference):
`h' to print hello, `q' to quit.
In the menu state, if the user presses `h, print out
Hello!
In the menu state, if the user presses `q, print out
quit.
and quits the menu state.
If not in the menu state, the TV does not respond to `h and `q.
The following is my code:
.data
menuLevel: .word 0
msg_tvworking:
.asciiz "tv is working\n"
msg_menu:
.asciiz "`h' to print hello, `q' to quit.\n"
msg_hello:
.asciiz "hello!\n"
msg_quit:
.asciiz "quit.\n"
main:
.text
.globl main
addi $s0, $0, 300 #s0: used in couting 10ms
mainloop:
# 1. read keyboard input, and process it
lui $t0, 0xFFFF # $t0 = 0xFFFF0000;
lw $t1, 0($t0)
andi $t1, $t1, 0x0001 $t1 # &= 0x00000001;
beq $t1, $0, mainloopnext1
lw $a0, 4($t0)
jal process_input
mainloopnext1:
# 2. update counter, check sleep timer
jal delay_10ms
# 3. $s0 as the 10ms counter, go from 0 to 299
addi $s0, $s0, -1
bne $s0, $0, mainloop
li $v0, 4
la $a0, msg_tvworking
syscall
addi $s0, $0, 300
j mainloop
li $v0,10 # exit
syscall
# -------------------delay_10ms:
li $t0, 1000
delay_10ms_loop:
addi $t0, $t0, -1
beq $t0, $0, delay_10ms_done
j delay_10ms_loop
delay_10ms_done:
jr $ra
# -------------------process_input:
la $t0, menuLevel
lw $t1, 0($t0)
bne $t1, $0, pi_menu_L_1
li $t0, 109 # comparing with the ascii of `m'
bne $a0, $t0, process_input_done
la $t0, menuLevel
li $t1, 1
sw $t1, 0($t0)
la $a0, msg_menu
li $v0, 4
syscall
j process_input_done
pi_menu_L_1:
li $t0, 104 # comparing with the
bne $a0, $t0, pi_menu_L_1_comp_q
la $a0, msg_hello
li $v0, 4
syscall
j process_input_done
pi_menu_L_1_comp_q:
li $t0, 113 # comparing with the
bne $a0, $t0, process_input_done
la $a0, msg_quit
li $v0, 4
syscall
la $t0, menuLevel
sw $0, 0($t0)
j process_input_done
process_input_done:
jr $ra
# --------------------
ascii of `h'
#
ascii of `q'
#