How can I read RTC in assembly?

Asked Feb 21 '23 at 01:04

Active Feb 21 '23 at 01:13

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I'm writing a bootloader. How can I read the current seconds range of the CMOS clock(0-59) in 16 bit x86 assembly?

I tried reading through this and I'm confused. https://wiki.osdev.org/CMOS#CMOS_Registers

edited Feb 21 '23 at 01:13

Peter Cordes

asked Feb 21 '23 at 01:04

sproutmaster

One of the answers on [How can I access system time using NASM?](https://stackoverflow.com/a/1465943) shows asm to read from the hardware RTC via `out` and `in` instructions, getting seconds, minutes, ..., year. – Peter Cordes Feb 21 '23 at 01:12
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The article you mentioned contains example how to read a CMOP register. What exactly confused you? Did you try to read CMOP register 0? What did you get? – dimich Feb 21 '23 at 01:15

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