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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!
42 lines
1.0 KiB
ArmAsm
42 lines
1.0 KiB
ArmAsm
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; Oliver Schmidt, 16.8.2018
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;
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; Common stuff for the clock routines
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;
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.include "cbm510.inc"
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.export TM, load_tenth
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.importzp sreg
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;----------------------------------------------------------------------------
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.code
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.proc load_tenth
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lda #<(100 * 1000 * 1000 / $10000)
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ldx #>(100 * 1000 * 1000 / $10000)
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sta sreg
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stx sreg+1
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lda #<(100 * 1000 * 1000)
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ldx #>(100 * 1000 * 1000)
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rts
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.endproc
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;----------------------------------------------------------------------------
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; TM struct with date set to 1970-01-01
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.data
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TM: .word 0 ; tm_sec
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.word 0 ; tm_min
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.word 0 ; tm_hour
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.word 1 ; tm_mday
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.word 0 ; tm_mon
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.word 70 ; tm_year
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.word 0 ; tm_wday
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.word 0 ; tm_yday
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.word 0 ; tm_isdst
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