1 | ; Project name : Assembly Library |
---|
2 | ; Description : Delay functions. |
---|
3 | |
---|
4 | ; Section containing code |
---|
5 | SECTION .text |
---|
6 | |
---|
7 | ;-------------------------------------------------------------------- |
---|
8 | ; Delay is always at least one millisecond since |
---|
9 | ; RTC resolution is 977 microsecs. |
---|
10 | ; |
---|
11 | ; Delay_MicrosecondsFromAX |
---|
12 | ; Parameters: |
---|
13 | ; AX: Number of microsecs to wait |
---|
14 | ; Returns: |
---|
15 | ; Nothing |
---|
16 | ; Corrupts registers: |
---|
17 | ; AX |
---|
18 | ;-------------------------------------------------------------------- |
---|
19 | ALIGN JUMP_ALIGN |
---|
20 | Delay_MicrosecondsFromAX: |
---|
21 | push dx |
---|
22 | push cx |
---|
23 | |
---|
24 | xor cx, cx |
---|
25 | xchg dx, ax ; Microsecs now in CX:DX |
---|
26 | mov ah, EVENT_WAIT ; Event Wait |
---|
27 | int BIOS_SYSTEM_INTERRUPT_15h |
---|
28 | sti ; XT BIOSes return with interrupt disabled |
---|
29 | |
---|
30 | pop cx |
---|
31 | pop dx |
---|
32 | mov ax, 1 ; Prepare to wait 1 timer tick |
---|
33 | jc SHORT Delay_TimerTicksFromAX ; Event Wait was unsupported or busy |
---|
34 | ret |
---|
35 | |
---|
36 | |
---|
37 | ;-------------------------------------------------------------------- |
---|
38 | ; First tick might take 0...54.9 ms and remaining ticks |
---|
39 | ; will occur at 54.9 ms intervals. |
---|
40 | ; |
---|
41 | ; Delay_TimerTicksFromAX |
---|
42 | ; Parameters: |
---|
43 | ; AX: Number of timer ticks to wait |
---|
44 | ; Returns: |
---|
45 | ; Nothing |
---|
46 | ; Corrupts registers: |
---|
47 | ; AX |
---|
48 | ;-------------------------------------------------------------------- |
---|
49 | ALIGN JUMP_ALIGN |
---|
50 | Delay_TimerTicksFromAX: |
---|
51 | push dx |
---|
52 | |
---|
53 | sti ; Make sure that interrupts are enabled |
---|
54 | xchg dx, ax |
---|
55 | call TimerTicks_ReadFromBdaToAX |
---|
56 | add dx, ax ; DX = end time |
---|
57 | .WaitLoop: |
---|
58 | call TimerTicks_ReadFromBdaToAX |
---|
59 | cmp ax, dx |
---|
60 | jb SHORT .WaitLoop ; Loop until end time is reached |
---|
61 | |
---|
62 | pop dx |
---|
63 | ret |
---|