$.$equ LEDS $,0$xf$0200000$ ; address of LED array

$.$equ SWITCH $,0$xf$0100000$ ; address of switches

reset:

li t$0,0$x$00$ ; initialize pattern to all off

sw t$0,$ LEDS ; display pattern

loop:

lw t$1,$ SWITCH ; read switches

andi t$1,$ t$1,0$x$0$f ; keep only lower $4$ bits

beq t$1,$ zero, all$\_$on ; if switches are $0,$ turn all LEDs on

beq t$1,$ t$2,$ loop ; if switches are the same as last time, do nothing

move t$2,$ t$1$ ; remember last switch value

li t$0,0$x$00$ ; initialize pattern to all off

andi t$3,$ t$1,0$x$01$ ; check bit $0$

beq t$3,$ zero, $.$odd ; if bit $0$ is $0,$ skip to odd check

$.$even: ori t$0,$ t$0,0$xaa ; turn on even LEDs

j $.$done

$.$odd: andi t$3,$ t$1,0$x$02$ ; check bit $1$

beq t$3,$ zero, $.$other ; if bit $1$ is $0,$ skip to other check

ori t$0,$ t$0,0$x$55$ ; turn on odd LEDs

j $.$done

$.$other: andi t$3,$ t$1,0$x$08$ ; check bit $3$

beq t$3,$ zero, $.$cycle ; if bit $3$ is $0,$ skip to cycle

li t$0,0$x$01$ ; initialize pattern to one on

$.$cycle: sll t$4,$ t$1,1$ ; shift left to create marquee pattern

or t$0,$ t$4$

$.$done: sw t$0,$ LEDS ; display pattern

j loop

all$\_$on: li t$0,0$xff ; turn all LEDs on

j loop