|
Routines |
| Prev: 49926 | Up: Map | Next: 50045 |
|
Used by the routine at ProcessScreenCharacter.
Copies the picture up one character row when the screen is being updated.
|
||||||||||
| UpdateScreenDisplay | 49942 | LD A,(49448) | Call 50148 if the screen flags is zero. | |||||||
| 49945 | AND A | |||||||||
| 49946 | CALL Z,50148 | |||||||||
| 49949 | PUSH BC | Save the registers and point HL at the second character row of the screen (16416). | ||||||||
| 49950 | PUSH HL | |||||||||
| 49951 | PUSH DE | |||||||||
| 49952 | LD HL,16416 | |||||||||
| 49955 | LD DE,16384 | Point the row copy at the top of the screen. | ||||||||
| 49958 | LD BC,17 | Take a length of 17 entries. | ||||||||
| 49961 | LD A,(49448) | Go to UpdateScreenDisplay_Loop with A=32 if the flag at 49448 is zero (otherwise use 16). | ||||||||
| 49964 | AND A | |||||||||
| 49965 | LD A,32 | |||||||||
| 49967 | JR Z,UpdateScreenDisplay_Loop | |||||||||
| 49969 | LD A,16 | Use 16 for the display. | ||||||||
| UpdateScreenDisplay_Loop | 49971 | PUSH HL | Save HL, DE and BC, and take a count of 8. | |||||||
| 49972 | PUSH DE | |||||||||
| 49973 | PUSH BC | |||||||||
| 49974 | LD C,8 | |||||||||
| UpdateScreenDisplay_KeepRowDestination | 49976 | PUSH HL | Keep the row, the destination and the count while this pixel line is copied. | |||||||
| 49977 | PUSH DE | |||||||||
| 49978 | PUSH BC | |||||||||
| 49979 | LD C,A | |||||||||
| 49980 | LDIR | Copy one row of the character being drawn onto the screen. | ||||||||
| 49982 | POP BC | Jump back to UpdateScreenDisplay_KeepRowDestination while the count is not finished. | ||||||||
| 49983 | POP DE | |||||||||
| 49984 | POP HL | |||||||||
| 49985 | INC H | |||||||||
| 49986 | INC D | |||||||||
| 49987 | DEC C | |||||||||
| 49988 | JR NZ,UpdateScreenDisplay_KeepRowDestination | |||||||||
| 49990 | POP BC | Restore the screen registers from the stack. | ||||||||
| 49991 | POP DE | |||||||||
| 49992 | POP HL | |||||||||
| 49993 | PUSH AF | And call AdvanceScreenPosition to advance the screen position. | ||||||||
| 49994 | CALL AdvanceScreenPosition | |||||||||
| 49997 | CALL AdvanceScreenPosition | Call AdvanceScreenPosition to advance screen position. | ||||||||
| 50000 | POP AF | |||||||||
| 50001 | DEC C | Jump back to UpdateScreenDisplay_Loop while the count is not finished. | ||||||||
| 50002 | JR NZ,UpdateScreenDisplay_Loop | |||||||||
| 50004 | CP 16 | Go to UpdateScreenDisplay_Next if it is 16. | ||||||||
| 50006 | JR Z,UpdateScreenDisplay_Next | |||||||||
| 50008 | LD HL,22560 | Point at the second and first attribute rows, ready to scroll the attributes up one row. | ||||||||
| 50011 | LD DE,22528 | |||||||||
| 50014 | LD BC,544 | Take 544 bytes, seventeen attribute rows. | ||||||||
| 50017 | LDIR | Scroll the attributes up one row. | ||||||||
| UpdateScreenDisplay_Next | 50019 | LD A,(49448) | Set B to 36 and jump to UpdateScreenDisplay_FillSpaces if the screen flag at 49448 is zero. | |||||||
| 50022 | AND A | |||||||||
| 50023 | LD B,36 | |||||||||
| 50025 | JR Z,UpdateScreenDisplay_FillSpaces | |||||||||
| 50027 | LD B,18 | Count 18. | ||||||||
| UpdateScreenDisplay_FillSpaces | 50029 | LD HL,20512 | Point HL at the screen address 20512 set C to 2 and take a space. | |||||||
| 50032 | LD C,2 | |||||||||
| 50034 | LD A,32 | |||||||||
| UpdateScreenDisplay_0 | 50036 | CALL PrintCharacter | Call PrintCharacter to print a space. | |||||||
| 50039 | DJNZ UpdateScreenDisplay_0 | Count the next entry and repeat from UpdateScreenDisplay_0. | ||||||||
| 50041 | POP DE | Restore the saved source, the saved pointer and the saved count from the stack. | ||||||||
| 50042 | POP HL | |||||||||
| 50043 | POP BC | |||||||||
| 50044 | RET | Return. | ||||||||
| Prev: 49926 | Up: Map | Next: 50045 |