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The CIA TOD only stores the time but not the date. Therefore the date set by clock_settime() ist just stored inside the C library for retrieval via clock_gettime(). The "very special" handling of 12AM/PM is based on https://groups.google.com/d/msg/comp.sys.cbm/ysVYSX4AMbc/vHrXCWEhCOUJ saying: ========== 24hr: Wr => Rd => Nx -------------------- 0 : 92 => 12 => 01 <= Switch from 00 to 01 (24-hour notation) 1 : 01 => 01 => 02 2 : 02 => 02 => 03 11 : 11 => 11 => 92 12 : 12 => 92 => 81 <= Switch from 12 to 13 (24-hour notation) 13 : 81 => 81 => 82 14 : 82 => 82 => 83 23 : 91 => 91 => 12 1. column ("24hr"): hour to be tested (decimal) 2. column ("Wr"): hour written to TOD register (BCD) 3. column ("Rd"): hour read from TOD register (BCD) immediately after writing the value in column 2 to see the conversion between AM/PM, if any 4. column ("Nx"): next hour (BCD) after the hour switch ========== Thanks Paul!
84 lines
1.9 KiB
ArmAsm
84 lines
1.9 KiB
ArmAsm
;
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; Stefan Haubenthal, 27.7.2009
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; Oliver Schmidt, 14.8.2018
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;
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; int clock_gettime (clockid_t clk_id, struct timespec *tp);
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;
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.include "time.inc"
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.include "c64.inc"
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.importzp sreg, tmp1, tmp2
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.import pushax, pusheax, tosmul0ax, steaxspidx, incsp1, return0
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.import TM, load_tenth
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;----------------------------------------------------------------------------
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.code
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.proc _clock_gettime
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jsr pushax
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jsr pushax
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lda CIA1_TODHR
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sed
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tax ; Save PM flag
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and #%01111111
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cmp #$12 ; 12 AM/PM
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bcc @L1
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sbc #$12
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@L1: inx ; Get PM flag
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bpl @L2
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clc
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adc #$12
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@L2: cld
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jsr BCD2dec
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sta TM + tm::tm_hour
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lda CIA1_TODMIN
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jsr BCD2dec
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sta TM + tm::tm_min
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lda CIA1_TODSEC
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jsr BCD2dec
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sta TM + tm::tm_sec
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lda #<TM
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ldx #>TM
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jsr _mktime
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ldy #timespec::tv_sec
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jsr steaxspidx ; Pops address pushed by 2. pushax
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jsr load_tenth
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jsr pusheax
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lda CIA1_TOD10
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ldx #>$0000
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jsr tosmul0ax
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ldy #timespec::tv_nsec
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jsr steaxspidx ; Pops address pushed by 1. pushax
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jsr incsp1
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jmp return0
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.endproc
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;----------------------------------------------------------------------------
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; dec = (((BCD>>4)*10) + (BCD&0xf))
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.proc BCD2dec
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tax
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and #%00001111
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sta tmp1
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txa
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and #%11110000 ; *16
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lsr ; *8
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sta tmp2
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lsr
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lsr ; *2
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adc tmp2 ; = *10
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adc tmp1
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rts
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.endproc
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