30 lines
709 B
ArmAsm
30 lines
709 B
ArmAsm
// #LAYOUT# STD * #TAKE
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// #LAYOUT# * KERNAL_0 #TAKE
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// #LAYOUT# * * #IGNORE
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//
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// Official Kernal routine, described in:
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//
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// - [RG64] C64 Programmers Reference Guide - page 291
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// - [CM64] Computes Mapping the Commodore 64 - page 232
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//
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// CPU registers that has to be preserved (see [RG64]): none
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//
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RDTIM:
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// Disable interrupts for the duration of the routine, to prevent
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// jiffy clock update while reeading its values
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sei
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// Store the jiffy clock state
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ldy TIME+0
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ldx TIME+1
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lda TIME+2
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// Enable interrupts. More elegant solution would be pha + sei + ... + pla,
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// but (checked by running a test program) original ROM routine always
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// leaves IRQs enabled.
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cli
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rts
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