| Line 1... |
Line 1... |
;
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;
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; rom06.s -- "crossed" echo with two terminals, polled
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; rom06.s -- "crossed" echo with two terminals, polled
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;
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;
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.set tba,0xF0300000 ; terminal base address
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.set tba0,0xF0300000 ; terminal base address 0
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.set tba1,0xF0301000 ; terminal base address 1
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add $8,$0,tba ; set terminal base address
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add $8,$0,tba0 ; set $8 to terminal base address 0
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add $9,$0,tba1 ; set $9 to terminal base address 1
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L1:
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L1:
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ldw $9,$8,0 ; load receiver status into $9
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ldw $10,$8,0 ; load receiver status into $10
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and $9,$9,1 ; check receiver ready
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and $10,$10,1 ; check receiver ready
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beq $9,$0,L3 ; not ready - check other terminal
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beq $10,$0,L3 ; not ready - check other terminal
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ldw $10,$8,4 ; load receiver data into $10
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ldw $11,$8,4 ; load receiver data into $11
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L2:
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L2:
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ldw $9,$8,24 ; load transmitter status into $9
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ldw $10,$9,8 ; load transmitter status into $10
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and $9,$9,1 ; check transmitter ready
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and $10,$10,1 ; check transmitter ready
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beq $9,$0,L2 ; loop while not ready
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beq $10,$0,L2 ; loop while not ready
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stw $10,$8,28 ; load char into transmitter data
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stw $11,$9,12 ; load char into transmitter data
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L3:
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L3:
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ldw $9,$8,16 ; load receiver status into $9
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ldw $10,$9,0 ; load receiver status into $10
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and $9,$9,1 ; check receiver ready
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and $10,$10,1 ; check receiver ready
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beq $9,$0,L1 ; not ready - check other terminal
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beq $10,$0,L1 ; not ready - check other terminal
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ldw $10,$8,20 ; load receiver data into $10
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ldw $11,$9,4 ; load receiver data into $11
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L4:
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L4:
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ldw $9,$8,8 ; load transmitter status into $9
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ldw $10,$8,8 ; load transmitter status into $10
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and $9,$9,1 ; check transmitter ready
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and $10,$10,1 ; check transmitter ready
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beq $9,$0,L4 ; loop while not ready
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beq $10,$0,L4 ; loop while not ready
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stw $10,$8,12 ; load char into transmitter data
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stw $11,$8,12 ; load char into transmitter data
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j L1 ; all over again
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j L1 ; all over again
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No newline at end of file
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No newline at end of file
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