48 lines
857 B
Plaintext
48 lines
857 B
Plaintext
//
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// This program let's the connected LEDs flash
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// with a duty cycle of 50% and
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// a period of approx. 1s
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//
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// r0: counter top
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// r1: counter
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// r2: LED address
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// r3: ones (0xFF)
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// r4: LED values
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irq0: br always >main
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nop
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// initialization constants
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.align
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sp_init: .word 0x200 // Stack pointer
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top: .word 16000000 // Counter top
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ptr: .word 0x0 // pointer to I/O device
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// main procedure
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main:
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// init registers
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ldr sp, >sp_init
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ldr r0, >top
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ldr r2, >ptr
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clr r1
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clr r3
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clr r4
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addi r3, -1
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// loop
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loop:
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cmp neq r1, r0
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br true >loop // loop if not equal (BDS!)
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addi r1, 1 // increment counter
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// counter top reached, set LEDs and clear counter
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xor r4, r4, r3 // invert last byte of r4
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st08 r2, r4 // write byte to I/O device
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br always >loop // branch back to loop (BDS!)
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clr r1 // reset counter
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nop
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nop
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