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28 lines
1.0 KiB
ArmAsm
28 lines
1.0 KiB
ArmAsm
.equ UART_BASE, 0x10000000 # a constant containing the base address for the uart that we will send data.
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# This UART is defined as a NS16550 Uart in https://www.qemu.org/docs/master/system/riscv/virt.html
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# UART16550 Core technical manual
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.section .text
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la a0, helloworld # Load address of string
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li a1, UART_BASE # Load uart tx base address. This will be used to send characters to the uart
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call puts # Print string
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loop: j loop # This loop never exits, so the program will just continue to loop.
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# This is function
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puts:
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# a0 - String address
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# a1 - UART Base address
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1: # While string bytes is no null
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lb t0, 0(a0) # Get byte at current string pos
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beq zero, t0, 2f # is null?
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sb t0, (a1) # Since not null write byte to port
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addi a0, a0, 1 # Implement string pointer moving us to the next character in the string.
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j 1b # Loop
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2: # String byte is null.
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ret
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.section .data
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helloworld: .string "Hello Chuck!\n"
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