Alisa Allaire
s
my_asm.s@0:208fc50f22f9, 2018-01-18 (annotated)
- Committer:
- aallaire3
- Date:
- Thu Jan 18 18:13:24 2018 +0000
- Revision:
- 0:208fc50f22f9
shshss
Who changed what in which revision?
| User | Revision | Line number | New contents of line |
|---|---|---|---|
| aallaire3 | 0:208fc50f22f9 | 1 | AREA asm_func, CODE, READONLY |
| aallaire3 | 0:208fc50f22f9 | 2 | EXPORT my_asm |
| aallaire3 | 0:208fc50f22f9 | 3 | |
| aallaire3 | 0:208fc50f22f9 | 4 | my_asm |
| aallaire3 | 0:208fc50f22f9 | 5 | |
| aallaire3 | 0:208fc50f22f9 | 6 | LDR R1, =0x2009C000 // pushbutton at p8 |
| aallaire3 | 0:208fc50f22f9 | 7 | LDR R2, =0x2009C040 // led at p21 |
| aallaire3 | 0:208fc50f22f9 | 8 | |
| aallaire3 | 0:208fc50f22f9 | 9 | MOV.W R3, #0x000020 ; 0x000020 = 1<<5 all "0"s with a "1" in bit 5 |
| aallaire3 | 0:208fc50f22f9 | 10 | ; value passed from C compiler code is in R0 - compare to a "0" |
| aallaire3 | 0:208fc50f22f9 | 11 | CMP R1, #0 ; value == 0 ? |
| aallaire3 | 0:208fc50f22f9 | 12 | ; (If-Then-Else) on next two instructions using equal cond from the zero flag |
| aallaire3 | 0:208fc50f22f9 | 13 | ITE EQ |
| aallaire3 | 0:208fc50f22f9 | 14 | ; STORE if EQ - clear led 1 port bit using GPIO FIOCLR register and mask |
| aallaire3 | 0:208fc50f22f9 | 15 | STREQ R3, [R2,#0x5C] ; if==0, clear LED1 bit |
| aallaire3 | 0:208fc50f22f9 | 16 | ; STORE if NE - set led 1 port bit using GPIO FIOSET register and mask |
| aallaire3 | 0:208fc50f22f9 | 17 | STRNE R3, [R1,#0x58] ; if==1, set LED1 bit |
| aallaire3 | 0:208fc50f22f9 | 18 | ; Return to C using link register (Branch indirect using LR - a return) |
| aallaire3 | 0:208fc50f22f9 | 19 | BX LR |
| aallaire3 | 0:208fc50f22f9 | 20 | END |