14a32f8e29
1. Add description of used register to remove TODO. 2. Refine all registers addr to HEX format.
80 lines
1.6 KiB
ArmAsm
80 lines
1.6 KiB
ArmAsm
/* https://github.com/cirosantilli/x86-bare-metal-examples#rct */
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/*
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* Reference: https://wiki.osdev.org/CMOS
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Register Contents Range
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0x00 Seconds 0–59
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0x02 Minutes 0–59
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0x04 Hours 0–23 in 24-hour mode,
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1–12 in 12-hour mode, highest bit set if pm
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0x07 Day of Month 1–31
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0x08 Month 1–12
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0x09 Year 0–99
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0x0A Status Register A
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RTC has an "Update in progress" flag (bit 7 of Status Register A).
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To read the time and date properly you have to wait until
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the "Update in progress" flag goes from "set" to "clear".
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*/
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.equ RTCaddress, 0x70
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.equ RTCdata, 0x71
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#include "common.h"
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BEGIN
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update_in_progress:
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mov $0x0A, %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 $0x00, %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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