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160 lines
5.3 KiB
NASM
160 lines
5.3 KiB
NASM
// A raster IRQ that opens the top/bottom border.
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/// @file
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/// Commodore 64 Registers and Constants
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/// @file
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/// The MOS 6526 Complex Interface Adapter (CIA)
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///
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/// http://archive.6502.org/datasheets/mos_6526_cia_recreated.pdf
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// Commodore 64 PRG executable file
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.file [name="irq-hyperscreen.prg", type="prg", segments="Program"]
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.segmentdef Program [segments="Basic, Code, Data"]
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.segmentdef Basic [start=$0801]
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.segmentdef Code [start=$80d]
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.segmentdef Data [startAfter="Code"]
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.segment Basic
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:BasicUpstart(main)
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/// Value that disables all CIA interrupts when stored to the CIA Interrupt registers
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.const CIA_INTERRUPT_CLEAR_ALL = $7f
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/// $D011 Control Register #1 Bit#3: RSEL Switch betweem 25 or 24 visible rows
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/// RSEL| Display window height | First line | Last line
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/// ----+--------------------------+-------------+----------
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/// 0 | 24 text lines/192 pixels | 55 ($37) | 246 ($f6)
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/// 1 | 25 text lines/200 pixels | 51 ($33) | 250 ($fa)
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.const VICII_RSEL = 8
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/// VICII IRQ Status/Enable Raster
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// @see #IRQ_ENABLE #IRQ_STATUS
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/// 0 | RST| Reaching a certain raster line. The line is specified by writing
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/// | | to register 0xd012 and bit 7 of $d011 and internally stored by
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/// | | the VIC for the raster compare. The test for reaching the
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/// | | interrupt raster line is done in cycle 0 of every line (for line
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/// | | 0, in cycle 1).
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.const IRQ_RASTER = 1
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/// Mask for PROCESSOR_PORT_DDR which allows only memory configuration to be written
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.const PROCPORT_DDR_MEMORY_MASK = 7
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/// RAM in 0xA000, 0xE000 I/O in 0xD000
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.const PROCPORT_RAM_IO = 5
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.const WHITE = 1
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.const RED = 2
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.const OFFSET_STRUCT_MOS6526_CIA_INTERRUPT = $d
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.const OFFSET_STRUCT_MOS6569_VICII_CONTROL1 = $11
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.const OFFSET_STRUCT_MOS6569_VICII_RASTER = $12
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.const OFFSET_STRUCT_MOS6569_VICII_IRQ_ENABLE = $1a
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.const OFFSET_STRUCT_MOS6569_VICII_BORDER_COLOR = $20
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.const OFFSET_STRUCT_MOS6569_VICII_IRQ_STATUS = $19
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/// Processor port data direction register
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.label PROCPORT_DDR = 0
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/// Processor Port Register controlling RAM/ROM configuration and the datasette
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.label PROCPORT = 1
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/// The VIC-II MOS 6567/6569
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.label VICII = $d000
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/// The CIA#1: keyboard matrix, joystick #1/#2
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.label CIA1 = $dc00
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/// The vector used when the HARDWARE serves IRQ interrupts
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.label HARDWARE_IRQ = $fffe
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.label GHOST_BYTE = $3fff
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.segment Code
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// Interrupt Routine 2
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irq_bottom_2: {
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sta rega+1
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// VICII->BORDER_COLOR = WHITE
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lda #WHITE
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sta VICII+OFFSET_STRUCT_MOS6569_VICII_BORDER_COLOR
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// VICII->CONTROL1 |= VICII_RSEL
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// Set screen height back to 25 lines (preparing for the next screen)
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lda #VICII_RSEL
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ora VICII+OFFSET_STRUCT_MOS6569_VICII_CONTROL1
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sta VICII+OFFSET_STRUCT_MOS6569_VICII_CONTROL1
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// VICII->IRQ_STATUS = IRQ_RASTER
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// Acknowledge the IRQ
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lda #IRQ_RASTER
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sta VICII+OFFSET_STRUCT_MOS6569_VICII_IRQ_STATUS
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// VICII->RASTER = 0xfa
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// Trigger IRQ 1 at line 0xfa
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lda #$fa
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sta VICII+OFFSET_STRUCT_MOS6569_VICII_RASTER
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// *HARDWARE_IRQ = &irq_bottom_1
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lda #<irq_bottom_1
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sta HARDWARE_IRQ
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lda #>irq_bottom_1
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sta HARDWARE_IRQ+1
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// VICII->BORDER_COLOR = RED
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lda #RED
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sta VICII+OFFSET_STRUCT_MOS6569_VICII_BORDER_COLOR
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// }
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rega:
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lda #0
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rti
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}
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// Interrupt Routine 1
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irq_bottom_1: {
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sta rega+1
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// VICII->BORDER_COLOR = WHITE
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lda #WHITE
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sta VICII+OFFSET_STRUCT_MOS6569_VICII_BORDER_COLOR
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// VICII->CONTROL1 &= (0xff^VICII_RSEL)
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// Set screen height to 24 lines - this is done after the border should have started drawing - so it wont start
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lda #$ff^VICII_RSEL
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and VICII+OFFSET_STRUCT_MOS6569_VICII_CONTROL1
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sta VICII+OFFSET_STRUCT_MOS6569_VICII_CONTROL1
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// VICII->IRQ_STATUS = IRQ_RASTER
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// Acknowledge the IRQ
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lda #IRQ_RASTER
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sta VICII+OFFSET_STRUCT_MOS6569_VICII_IRQ_STATUS
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// VICII->RASTER = 0xfd
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// Trigger IRQ 2 at line 0xfd
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lda #$fd
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sta VICII+OFFSET_STRUCT_MOS6569_VICII_RASTER
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// *HARDWARE_IRQ = &irq_bottom_2
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lda #<irq_bottom_2
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sta HARDWARE_IRQ
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lda #>irq_bottom_2
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sta HARDWARE_IRQ+1
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// VICII->BORDER_COLOR = RED
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lda #RED
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sta VICII+OFFSET_STRUCT_MOS6569_VICII_BORDER_COLOR
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// }
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rega:
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lda #0
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rti
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}
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main: {
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// *GHOST_BYTE = 0
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lda #0
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sta GHOST_BYTE
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// asm
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sei
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// CIA1->INTERRUPT = CIA_INTERRUPT_CLEAR_ALL
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// Disable CIA 1 Timer IRQ
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lda #CIA_INTERRUPT_CLEAR_ALL
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sta CIA1+OFFSET_STRUCT_MOS6526_CIA_INTERRUPT
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// VICII->CONTROL1 &= 0x7f
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// Set raster line to 0xfa
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lda #$7f
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and VICII+OFFSET_STRUCT_MOS6569_VICII_CONTROL1
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sta VICII+OFFSET_STRUCT_MOS6569_VICII_CONTROL1
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// VICII->RASTER = 0xfa
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lda #$fa
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sta VICII+OFFSET_STRUCT_MOS6569_VICII_RASTER
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// VICII->IRQ_ENABLE = IRQ_RASTER
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// Enable Raster Interrupt
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lda #IRQ_RASTER
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sta VICII+OFFSET_STRUCT_MOS6569_VICII_IRQ_ENABLE
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// *HARDWARE_IRQ = &irq_bottom_1
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// Set the IRQ routine
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lda #<irq_bottom_1
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sta HARDWARE_IRQ
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lda #>irq_bottom_1
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sta HARDWARE_IRQ+1
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// *PROCPORT_DDR = PROCPORT_DDR_MEMORY_MASK
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// no kernal or BASIC rom visible
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lda #PROCPORT_DDR_MEMORY_MASK
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sta.z PROCPORT_DDR
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// *PROCPORT = PROCPORT_RAM_IO
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lda #PROCPORT_RAM_IO
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sta.z PROCPORT
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// asm
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cli
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__b1:
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jmp __b1
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}
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