8687f3f8f4
Thanks to Kyle Lemons for the inspiration and original design. The implementation in this commit is very different however, building on top of the software vectoring needed in RISC-V. The result is a flexible interrupt handler that does not take up any RAM for configuration.
45 строки
1,6 КиБ
ArmAsm
45 строки
1,6 КиБ
ArmAsm
.section .init
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.global _start
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.align
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.arm
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_start:
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b start_vector
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.fill 156,1,0 // Nintendo Logo Character Data (8000004h)
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.fill 16,1,0 // Game Title
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.byte 0x30,0x31 // Maker Code (80000B0h)
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.byte 0x96 // Fixed Value (80000B2h)
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.byte 0x00 // Main Unit Code (80000B3h)
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.byte 0x00 // Device Type (80000B4h)
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.fill 7,1,0 // unused
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.byte 0x00 // Software Version No (80000BCh)
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.byte 0xf0 // Complement Check (80000BDh)
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.byte 0x00,0x00 // Checksum (80000BEh)
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start_vector:
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// Configure stacks
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mov r0, #0x12 // Switch to IRQ Mode
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msr cpsr, r0
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ldr sp, =_stack_top_irq // Set IRQ stack
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mov r0, #0x1f // Switch to System Mode
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msr cpsr, r0
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ldr sp, =_stack_top // Set user stack
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// Configure interrupt handler
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mov r0, #0x4000000 // REG_BASE
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ldr r1, =handleInterruptARM
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str r1, [r0, #-4] // actually storing to 0x03007FFC due to mirroring
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// Enable interrupts
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mov r1, #1
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str r1, [r0, #0x208] // 0x04000208 Interrupt Master Enable
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// Jump to user code (switching to Thumb mode)
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ldr r3, =main
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bx r3
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// Small interrupt handler that immediately jumps to a function defined in the
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// program (in Thumb) for further processing.
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handleInterruptARM:
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ldr r0, =handleInterrupt
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bx r0
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