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How can I access system time using NASM?

Answer 1

+2 A:

%define RTCaddress  0x70
%define RTCdata  0x71

;Get time and date from RTC

.l1:    mov al,10   ;Get RTC register A
    out RTCaddress,al
    in al,RTCdata
    test al,0x80   ;Is update in progress?
    jne .l1    ; yes, wait

    mov al,0   ;Get seconds (00 to 59)
    out RTCaddress,al
    in al,RTCdata
    mov [RTCtimeSecond],al

    mov al,0x02   ;Get minutes (00 to 59)
    out RTCaddress,al
    in al,RTCdata
    mov [RTCtimeMinute],al

    mov al,0x04   ;Get hours (see notes)
    out RTCaddress,al
    in al,RTCdata
    mov [RTCtimeHour],al

    mov al,0x07   ;Get day of month (01 to 31)
    out RTCaddress,al
    in al,RTCdata
    mov [RTCtimeDay],al

    mov al,0x08   ;Get month (01 to 12)
    out RTCaddress,al
    in al,RTCdata
    mov [RTCtimeMonth],al

    mov al,0x09   ;Get year (00 to 99)
    out RTCaddress,al
    in al,RTCdata
    mov [RTCtimeYear],al

    ret

This uses NASM, and is from here.

Kyle Rozendo 2009-09-23 13:17:34

I'm a little confused. Is this working on the assumption that the poster is using windows?

BigBeagle 2009-09-23 13:23:56

Should work for any OS on x86 that maintains its system date/time.

Kyle Rozendo 2009-09-23 13:27:35

Just tried -- Unfortunately, "out RTCaddress,al" fails on Vista64 because of privilege level.

PhiS 2009-09-23 21:09:05

Ah, I don't really know then. As I said, I this should work on x86, not x64, let alone with Vista's glorious security, hehe.

Kyle Rozendo 2009-09-24 17:01:37

Answer 2

A:

You could make a call to interrupt 1Ah to get the clock ticks since midnight.

here are some people talking about formating the time from ticks

Sorskoot 2009-09-23 13:19:38

On which systems will or won't this work?

PhiS 2009-09-23 18:43:15

I only have experience with these interrupts on DOS on a x86. They're old, but I'm not sure if they'll work on other platforms. Have a look at this, maybe it helps: http://linux.ucla.edu/LDP/LDP/khg/HyperNews/get/khg/117/1/1/1.html

Sorskoot 2009-09-23 19:10:52

Just tried on Vista. Doesn't seem to work there.

PhiS 2009-09-23 20:59:39

Answer 3

A:

I'd say, depending on what platform you're on, you'll have to use an OS function.

On windows, try GetSystemTime. On linux, try gettimeofday - see related question here.

PhiS 2009-09-23 21:18:14

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