DB   Start, KeyInterrupt, 'ABC', 123
     NOP
     NOP
     NOP
     
     VAR  DeviceConsole 1
     VAR  ConsoleReadChar 0
     VAR  ConsoleWriteChar 0
     
     VAR  DeviceKeyboard 2
     
     VAR  DeviceScreen 3
     VAR  ScreenGetWidth 0
     VAR  ScreenGetHeight 1
     VAR  ScreenSetAddr 0
     VAR  ScreenWrite 1
     
     ORG 16
Start:
 
; Example code
;    NOP
;LOOP: 
    ;SET  R0, 123
    ;SET  R1, 1024
    ;SET  R2, 32
    ;ST   R2, R1
    ;JNZ  R0, LOOP
    ;SET  R0, 124
    ;JNZ  R0, LOOP2
    ;SET  R0, 6
LOOP2:
    SET  R0, Hello
    SET  R1, 12
    CALL WriteStr
    
;    SET  R0, 0
;    SET  R1, 128
;    SET  R2, 16
;    CALL LDIR
    
;    SET  R0, 256
;    SET  R1, 16
;    SET  R2, 127
;    CALL SETR
    
    CALL ClearScreen
    
System:
    HALT
    JP   System
    

    
LDIR:
    PUSH R3
LDIR_LOOP:
    LD   R3, (R0)
    ST   (R1), R3
    INC  R0
    INC  R1
    DEC  R2
    JNZ  R2, LDIR_LOOP
    POP  R3
    RET
    
SETR:
    ST   (R0), R2
    INC  R0
    DEC  R1
    JNZ  R1, SETR
    RET

WriteStr:
    PUSH R2
    PUSH R3
    PUSH R4
    SET  R3, ConsoleWriteChar
    SET  R4, DeviceConsole
WriteStrLoop:
    LD   R2, (R0)
    OUT  (R4: R3), R2
    INC  R0
    DEC  R1
    JNZ  R1, WriteStrLoop
    POP  R4
    POP  R3
    POP  R2
    RET
        
ClearScreen:
    PUSH R0
    PUSH R1
    PUSH R2
    PUSH R3
    SET  R0, ScreenSetAddr
    SET  R1, 0  
    SET  R3, DeviceScreen
    OUT  (R3: R0), R1
    SET  R0, ScreenGetWidth
    IN   R1, (R3: R0)
    SET  R0, ScreenGetHeight
    IN   R2, (R3: R0)
    MUL  R2, R1
    SET  R0, ScreenWrite
    SET  R1, 120
ClearScreenLoop:
    OUT  (R3: R0), R1
    DEC  R2
    JNZ  R2, ClearScreenLoop
    POP  R3
    POP  R2
    POP  R1
    POP  R0
    RET
    
Hello:
    DB   'Hello friend'

KeyInterrupt:
    ; Echo key
    PUSH R3
    PUSH R2
    PUSH R4
    SET  R4, DeviceConsole
    SET  R3, ConsoleReadChar
    IN   R2, (R4: R3)
    SET  R3, ConsoleWriteChar
    OUT  (R4: R3), R2
    POP  R4
    POP  R2
    POP  R3
    RET

Test:
     LDI R0, (R1 + 1)
     STI (R1 + 12), R2