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added comments that try to explain video page flip

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This commit is contained in:
Markus Fröschle
2013-10-30 14:19:59 +00:00
parent 574b62462b
commit 1d45c22e04
3 changed files with 181 additions and 16 deletions
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37
sources/exceptions.S
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@@ -608,7 +608,7 @@ irq6: // MFP interrupt from FPGA
add.l #std_mmutr,d0
move.l d3,d1 // page 0?
beq irq6_sca_pn0 // ja ->
add.l #copyback_mmudr,d1 // sonst page cb
add.l #copyback_mmudr,d1 // sonst page cb
bra irq6_sca_pn1c
irq6_sca_pn0:
add.l #writethrough_mmudr|MCF_MMU_MMUDR_LK,d1 // page wt and locked
@@ -891,7 +891,9 @@ psc3_fertig:
RTE
/*
* general purpose timer 0 (GPT0): video change, later also others
* general purpose timer 0 (GPT0): video change, later also others. GPT0 is used as
* input trigger. It is connected to the TIN0 signal of the FPGA and triggers everytime
* vbasehi is written to, i.e. when the video base address gets changed
*/
handler_gpt0:
move #0x2700,sr // disable interrupts
@@ -900,31 +902,34 @@ handler_gpt0:
movem.l d0-d4/a0-a1,(a7)
mvz.b vbasehi,d0 // screen base address high
cmp.w #2,d0 // lower than 0x200000?
blt video_chg_end // yes
cmp.w #0xd0,d0 // 0xd00000? - normal Falcon video area, map to 60d00000 (FPGA video memory)
cmp.w #2,d0 // screen base lower than 0x20000?
blt video_chg_end // yes, do nothing
cmp.w #0xd0,d0 // lower than 0xd00000? - normal Falcon video area, mapped
// to 60d00000 (FPGA video memory)
blt sca_other //
lea MCF_SLT0_SCNT,a0
move.l (a0),_video_sbt // save time
// FIXME: don't we need to get out here?
sca_other:
lsl.l #8,d0 // build screen start address from Atari register contents
lsl.l #8,d0 // build new screen start address from Atari register contents
move.b 0xffff8203,d0 // mid byt
lsl.l #8,d0
move.b 0xffff820d,d0 // low byt
move.l d0,d3
video_chg_1page:
// test ob page schon gesetzt
// check if page is already marked as video page
moveq #20,d4
move.l d0,d2
lsr.l d4,d2 // neue page
lsr.l d4,d2 // new page
move.l _video_tlb,d4
bset.l d2,d4 // setzen als ge<EFBFBD>ndert
bne video_chg_2page // schon gesetzt gewesen? ja->weg
bset.l d2,d4 // set as changed
bne video_chg_2page // was it set already?
move.l d4,_video_tlb
bsr cpusha // cache leeren
bsr cpusha // clear cache
video_copy_data:
move.l d4,_video_tlb
@@ -932,7 +937,7 @@ video_copy_data:
move.l d0,a0
move.l a0,a1
add.l #0x60000000,a1
move.l #0x10000,d4 // die ganze page
move.l #0x10000,d4 // whole page
#define _DO_CPU_COPY
#ifndef _DO_CPU_COPY
@@ -968,7 +973,7 @@ video_copy_data:
#else
video_copy_data_loop:
move.l (a0)+,(a1)+
move.l (a0)+,(a1)+ // copy video page contents to real screen
move.l (a0)+,(a1)+
move.l (a0)+,(a1)+
move.l (a0)+,(a1)+
@@ -977,9 +982,9 @@ video_copy_data_loop:
#endif
// eintrag suchen
move.l d0,MCF_MMU_MMUAR // addresse
move.l d0,MCF_MMU_MMUAR // adress
move.l #0x106,d4
move.l d4,MCF_MMU_MMUOR // suchen -> schl<EFBFBD>gt neuen vor wenn keiner
move.l d4,MCF_MMU_MMUOR // search -> new one will be offered if not found
nop
move.l MCF_MMU_MMUOR,d4
clr.w d4
@@ -994,7 +999,7 @@ video_copy_data_loop:
move.l d2,MCF_MMU_MMUOR // setzen vidoe maped to 60xxx only data
nop
video_chg_2page:
// test ob evt. anschliessende page gesetzt werden muss
// test of adjacent page is needed also
move.l d3,d0
mvz.w 0xffff8210,d4 // byts pro zeile
mvz.w 0xffff82aa,d2 // zeilen ende