; the 24x4 character LCD has on each position 6x8 pixels
; the left 12 columns (0-11) are addressed from left to right
; but the right 12 column are logical the rows 4-7 and these
; columns are addressed by 0-11 from right to left!
;
843E: CP  e8H
      JR NC,+44 [846E]
      LD B,A
      LD A,(7932H)
      BIT 7,A
      JR NZ,+3 [844D]
      LD A,B
      JR +33 [846E]
844D: LD A,B
      CP 4cH
8450: JR NZ,+4 [8456]
      LD A,4cH
      JR +24 [846E]
8456: CP 90H
      JR C,+20 [846E]
      CP d0H
      JR C,+16 [846E]
      CP e1H
8460: JR C,+12 [846E]
      JR +10 [846E]
8464: ADD 16
      JR -42   [843E]
;
; ENTRY point of 'char out'   character to display is in A
; character values < 32 are all mapped to 10H
; row position to display on LCD in D: valid range 0-3
; column position to display on LCD in E: valid range 0-23
;
8468: SUB 32
      JR NC,-8 [8464]
      LD A,16
846E: LD C,A
      IN A,(19)
      PUSH AF
      LD A,4
      OUT (19),A
      LD A,E    ; column
      CP 12
      JR NC,+73
847B: IN A,(59)
      AND  80H
      JR NZ,-6
      LD A,(790D)
      ADD A,D   ; row
      OR b8H
      OUT (58),A
      LD A,E
      ADD A,A
      ADD A,A
      ADD E     ; 5*column
      OR 40H
      LD B,A
8490: IN A,(59)
      AND 80H
      JR NZ,-6 [8490]
      LD A,B
      OUT (58),A
      LD B,0
      LD H,B
      LD L,C
      ADD HL,HL
      ADD HL,HL
      ADD HL,BC      ; HL = 5*BC = 5 * char
      LD BC,(ffd4h)  ; font table offset
      ADD HL,BC
      BIT 2,D
      JR Z,+1
      DEC HL
      LD B,5
84AC: IN A,(59)
      AND 80H
      JR NZ,-6
      LD A,(HL)
      OUT (5A),A
      BIT 2,D
      JR NZ,+8 [84C1]
      INC HL
84BA: DJNZ -16 [84AC]
      POP AF
      OUT (19),A
      NOP
      RET
84C1: DEC HL
      JR -10 [84BA]
84C4: LD A,17H
      SUB E
      SET 2,D
      INC C
      JR -82 [847B]
;
; Entry Point for "String out" with wrap lines and scrolling if necessary
; in HL ist start address of string and in B the length of the string
; in D the start row (0-3) and in E the start column (0-23) of the string
;
84CD: LD C,0
84CF: PUSH HL
      PUSH DE
      PUSH BC
      LD A,(HL) 
      CALL 8468
      POP BC
      POP DE
      POP HL
      DEC B
      RET Z
      INC HL
      INC E
      LD A,E
      CP 24
84E0: JR NZ,-19 [84CF]
      LD E,0
      INC D
      LD A,D
      CP 4
      JR NZ,-27 [84CF]
      INC C
      PUSH HL
      PUSH BC
      CALL 84F7
84F0: POP BC
      POP HL
      LD  DE,300H
      JR -40   [84CF]
;  Entry point to scroll up display one line
84F7: LD HL,8528H    
      CALL 8550     ; clear the symbols in the display
      INC A         ; increase logical display offset
      AND 7
8500: LD (790D),A   ; now display scrolls one line up
      CALL 8712
      CALL 854D     ; set the symbols in the display
      LD L,3
850B: CALL 8543
      ADD A,L
      CALL 852C
      LD A,40H
      OUT (58),A
      LD B,60
8518: CALL 8530
      XOR A
      OUT (5A),A
      DJNZ -8 [8518]
8520: LD A,L
      LD L,7
      CP 3
      JR Z,-28 [850B]
      RET
8528: 00
      00
      00
      00
852C: OR b8H
852E: OUT (58),A      
8530: IN A,(59)
      AND 80H
      JR NZ,-6
      RET
8537: CALL 852C
      LD A,7cH   ; 01111100
      CALL 852E
      LD A,(HL)
      OUT (5A),A
      INC HL
8543: IN A,(59)
      AND 80H
      JR NZ,-6 [8543]
      LD A,(790D)
      RET
854D: LD HL,7901
8550: CALL 8543 
      CALL 8537
      ADD A,3
      CALL 8537
      ADD A,4
      CALL 8537
      ADD A,7
      JR -45 [8537]

; Entry Point for B-times character in A output (line wrapping, but no scroll)
; in D the start row (0-3) and in E the start column (0-23) of the string
;
86B3: LD C,A
86B4: PUSH DE
      PUSH BC
      LD A,C
      CALL 8468
      POP BC
      POP DE
      DEC B
      RET Z
      INC E
      LD A,E
      CP 24
      JR NZ,-16 [86B4]
      LD E,0
      INC D
      LD A,D
      CP 4
      JR NZ,-24 [86B4]
      RET

8712: ADD A,A
      ADD A,A
      ADD A,A
      OR c0h      ; 11000000 + 8*row
      OUT (58),A
      RET