Tried interrupts with IM 2

src/test/int_tab.asm

@@ -1,15 +1,67 @@
 ;;Tests all interrupt vectors to find which interrupt value is used querying the Keyboard in IM2
-        ORG     100H        ;Tell the assembler to start at addr 0x100
-START:  IM      2           ;Set interrupt mode 2
-        LD      HL,GREET    ;Load the start addr. of the banner
-        LD      B,16H       ;Set the length of the banner text
-        LD      DE,0H       ;Place curser in the top left
-        CALL    84CDH       ;Call system str_out
-        LD      A,INTTBL/256;Load the vectors for the interrupt table
-        LD      I,A         ;Load the interrupt table to I
-        EI                  ;Make sure interrupt are allowed
-LOOP:   HALT                ;Halt the CPU and wait for interrupts
-        JR      LOOP        ;Stay in the loop
-        RET                 ;Return to original caller
-GREET:  DB          'Test for keyboard int.'
-        END         
+        ORG     100H        ;Start at address 0x100
+;;setup interrupt vector table. Vector itself will be at 0x2020
+        DI                  ;disable interrupts
+        IM      2           ;set interrupt mode 2
+        LD      A,03H       ;Load the most significant byte of
+        LD      I,A         ;the vector table address to I
+        LD      HL,0300H    ;Start address of the interrupt vector table
+        LD      E,L         ;Fills the LSB to E
+        LD      D,H         ;and the MSB to D
+        INC     DE          ;increase DE
+        LD      (HL),02H    ;Load half of the vector to (HL)
+        LD      BC,0100H    ;257, because of the case where 8-bit vector is 0xFF
+        LDIR                ;walk over the following bytes
+        EI                  ;reenable interrupts
+        LD      HL,GREET    ;Load the start of a banner
+        LD      B,15H       ;The length of the string
+        LD      DE,0H       ;start in the topleft corner
+        CALL    84CDH       ;Call str_out
+MLOOP:  HALT                ;Stop and wait for interrupts
+        POP     AF          ;Get the result of the interrupt from the stack
+        CP      51H         ;Checks if the pressed key was "ON/Break"
+        RET     Z           ;If the key was "ON" end the program.
+        LD      HL,BUF      ;Load the buffer addess
+        CALL    BTOHEX      ;Convert the byte in A into a HEX-string and store it at BUF
+        LD      B,2         ;Set the length of BUF
+        LD      DE,15H      ;Position cursor in row 0, col 22
+        CALL    84CDH       ;Print the Keycode
+        JR      MLOOP       ;Stay in the loop
+        RET        
+;;Convert the contents of A into a hex-string and stores the result in the buffer pointed in HL
+BTOHEX: PUSH    AF          ;Store A onto the stack for later use
+        LD      B,4         ;Init a loop for shifting the register
+LP1:    SRL     A           ;Shift the MSN down to the least significant Nibble
+        DJNZ    LP1         ;Shift again, until all 4 bits where shifted.
+        CALL    HEXDGT      ;Converts the LSN to hex
+        INC     HL          ;Point HL to the next byte in buffer
+        POP     AF          ;Retrieve the original A
+        AND     0FH         ;Cut the first digit of the hex no.
+        CALL    HEXDGT      ;Call HEXDIGIT again for the second digit.
+        LD      HL,BUF      ;Restore the buffer address
+        RET
+;;Converts the least significant nibble in A into a ASCII hex-digit and stores the result
+HEXDGT: CP      0AH         ;Check if the number is smaller than 10
+        JR      C,SKIP      ;Skip the next instruction, if it is
+        ADD     A,07H       ;If the value is >10, we need to skip the chars between '9' and 'A'
+SKIP:   ADD     A,30H       ;Converts the number into its ASCII digit
+        LD      (HL),A      ;Store the digit in the correct location.
+        RET
+GREET:  DB      'Test keyboard input: '
+BUF:    DS      2           ;Define a 2 byte buffer to store the keycode in ASCII
+        ORG     0202H       ;Start address of the interrupt handler
+        DI                  ;turn off the interrupts
+        EX      AF,AF'      ;store the AF register
+        EXX                 ;store the register states
+        IN      A,(10H)     ;read interrupt reasons from I/O port
+        SRA     A           ;test for bit 0 set
+        JR      NC,ENDI     ;End the routine, of the reason for interrupt was not the keyboard
+        CALL    8881H       ;Check the pressed button
+        PUSH    AF          ;The keycode is in A, push that to the stack as result.   
+ENDI:   EXX                 ;restore the register states
+        EX      AF,AF'      ;restore AF register
+        EI                  ;enable interrupts
+        RETI                ;return
+        ORG     0300H       ;start of the vector table
+        DS      0100H       ;reserve 256 bytes
+        END                 ;End of memory