Question

Write an LC-3 program that will repeatedly read a character from the keyboard. For each character read in, your program will print a neat message that echoes the input value, and the ASCII character code of the input character in hexadecimal. It will run forever: no HALT or End of processing is required.

For example:

Please press a key:

You pressed 'z' which is x7A

Please press a key:

You pressed '@' which is x40

Please press a key:

You pressed 'O' which is x4F

Please press a key:

You pressed '2' which is x32

Please press a key:

You pressed ' ' which is x20

..

Answer 1

Given Data:

Please press a key:

You pressed 'z' which is x7A

Please press a key:
You pressed '@' which is x40
Please press a key:
You pressed 'O' which is x4F
Please press a key:
You pressed '2' which is x32
Please press a key:
You pressed ' ' which is x20

Program:

.ORIG   x3000

        LD R1, NEG     ; Load negative of count to R1

POLL1 (a)LDI R2, KSR    ; Read Keyboard status register into R2

      (b)BRzp POLL1     ; If "ready bit" not set, branch to POLL1

      (c)LDI R0, KDR    ; Read input character from Keyboard data register to R0

       

POLL2 (d)LDI R2, DSR    ; Read Display status register into R2

      (e)BRzp POLL2     ; If "ready bit" not set, branch to POLL2

      (f)STI R0, DDR    ; Write output character from R0 to Display data register

       

        ADD R0, R0, #1 ; Increment the charater

        ADD R1, R1, #1 ; Increment count

        BRn POLL2

        HALT

NEG     .FILL   xFFF6   ; -x000A

KSR     .FILL   xFE00   ; Keyboard status register location

KDR     .FILL   xFE02   ; Keyboard data register location

DSR     .FILL   xFE04   ; Display status register location

DDR     .FILL   xFE06   ; Display data register location

        .END