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46 lines
2.6 KiB
ArmAsm
46 lines
2.6 KiB
ArmAsm
/* -----------------------------------------------------------------------------
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* Project Name : Architectures of Processor Systems (APS) lab work
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* Organization : National Research University of Electronic Technology (MIET)
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* Department : Institute of Microdevices and Control Systems
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* Author(s) : Andrei Solodovnikov
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* Email(s) : hepoh@org.miet.ru
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See https://github.com/MPSU/APS/blob/master/LICENSE file for licensing details.
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* ------------------------------------------------------------------------------
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*/
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_start:
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# Initialize register values
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0: 050000b7 li x1 , 0x05000000 # save UART RX base address
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4: 04000137 li x2 , 0x04000000 # save hex-controller base address
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8: 0001c1b7 li x3 , 0x0001c200 # set baud rate to 115200
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c: 20018193
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10: 0030a623 sw x3 , 0x0c(x1)
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14: 00100213 li x4 , 0x00000001 # set parity bit
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18: 0040a823 sw x4 , 0x10(x1)
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1c: 03400293 la x5, trap_handler # the la pseudo-instruction loads a number similarly to li,
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20: 00028293 # but in the case of la the number is the address
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# of the specified location (the trap handler address);
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# this pseudo-instruction will be split into two
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# instructions: lui and addi
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24: 30529073 csrw mtvec, x5 # set the interrupt vector
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28: 000102b7 li x5 , 0x00010000 # prepare the interrupt mask for the single
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# (zeroth) input
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2c: 30429073 csrw mie, x5 # load the mask into the mask register
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# Call main function
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main:
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30: 00000063 beq x0, x0, main # infinite loop, equivalent to while (1);
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# TRAP HANDLER
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# Without external intervention the processor will never reach the instructions below;
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# however, upon an interrupt the program counter will be loaded with the address of
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# the first instruction below.
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# Save used registers to the stack
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trap_handler:
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34: 0000a383 lw x7, 0(x1) # load the received byte
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38: 00700333 add x6, x0, x7 # duplicate the scan code
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3c: 00435313 srl x6, x6, 4 # shift right by 4 to obtain the upper nibble
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40: 00612223 sw x6, 4(x2) # write upper nibble to the first seven-segment display
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44: 00f3f393 andi x7, x7, 0xf # mask with f to obtain the lower nibble
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48: 00712023 sw x7, 0(x2) # write lower nibble to the zeroth seven-segment display
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4c: 30200073 mret
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