92 lines
1.5 KiB
ArmAsm
92 lines
1.5 KiB
ArmAsm
/*
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# in RTC
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Real time clock.
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Gives wall time with precision of seconds.
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Uses a separate battery to keep going.
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http://stackoverflow.com/questions/1465927/how-can-i-access-system-time-using-nasm
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http://wiki.osdev.org/RTC
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http://wiki.osdev.org/CMOS
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Kenrel 4.2 usage: https://github.com/torvalds/linux/blob/v4.2/arch/x86/kernel/rtc.c#L121
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## Milliseconds
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Not possible. Must use the PIT.
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## Time zone
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QEMU uses UTC.
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*/
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#include "common.h"
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BEGIN
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/*
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TODO what do those numbers mean? Where is this all documented?
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*/
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.equ RTCaddress, 0x70
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.equ RTCdata, 0x71
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update_in_progress:
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mov $10, %al
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out %al, $RTCaddress
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in $RTCdata, %al
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testb $0x80, %al
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jne update_in_progress
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/* Second. */
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mov $0, %al
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out %al, $RTCaddress
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in $RTCdata, %al
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/* Only print if second changed. */
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cmp %al, %cl
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je update_in_progress
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mov %al, %cl
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PRINT_HEX <%al>
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PUTC
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/* Minute. */
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mov $0x02, %al
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out %al, $RTCaddress
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in $RTCdata, %al
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PRINT_HEX <%al>
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PUTC
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/* Hour. */
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mov $0x04, %al
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out %al, $RTCaddress
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in $RTCdata, %al
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PRINT_HEX <%al>
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PUTC
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/* Day. */
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mov $0x07, %al
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out %al, $RTCaddress
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in $RTCdata, %al
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PRINT_HEX <%al>
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PUTC
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/* Month. */
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mov $0x08, %al
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out %al, $RTCaddress
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in $RTCdata, %al
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PRINT_HEX <%al>
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PUTC
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/* Year. */
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mov $0x09, %al
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out %al, $RTCaddress
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in $RTCdata, %al
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PRINT_HEX <%al>
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PRINT_NEWLINE
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jmp update_in_progress
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