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Routines |
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Used by the routine at ProcessScreenCharacter.
Copies the picture up one character row when the screen is being updated.
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| UpdateScreenDisplay | C316 | LD A,($C128) | Call C3E4 if the screen flags is zero. | |||||||
| C319 | AND A | |||||||||
| C31A | CALL Z,$C3E4 | |||||||||
| C31D | PUSH BC | Save the registers and point HL at the second character row of the screen (4020). | ||||||||
| C31E | PUSH HL | |||||||||
| C31F | PUSH DE | |||||||||
| C320 | LD HL,$4020 | |||||||||
| C323 | LD DE,$4000 | Point the row copy at the top of the screen. | ||||||||
| C326 | LD BC,$0011 | Take a length of 11 entries. | ||||||||
| C329 | LD A,($C128) | Go to UpdateScreenDisplay_Loop with A=20 if the flag at C128 is zero (otherwise use 10). | ||||||||
| C32C | AND A | |||||||||
| C32D | LD A,$20 | |||||||||
| C32F | JR Z,UpdateScreenDisplay_Loop | |||||||||
| C331 | LD A,$10 | Use 10 for the display. | ||||||||
| UpdateScreenDisplay_Loop | C333 | PUSH HL | Save HL, DE and BC, and take a count of 08. | |||||||
| C334 | PUSH DE | |||||||||
| C335 | PUSH BC | |||||||||
| C336 | LD C,$08 | |||||||||
| UpdateScreenDisplay_KeepRowDestination | C338 | PUSH HL | Keep the row, the destination and the count while this pixel line is copied. | |||||||
| C339 | PUSH DE | |||||||||
| C33A | PUSH BC | |||||||||
| C33B | LD C,A | |||||||||
| C33C | LDIR | Copy one row of the character being drawn onto the screen. | ||||||||
| C33E | POP BC | Jump back to UpdateScreenDisplay_KeepRowDestination while the count is not finished. | ||||||||
| C33F | POP DE | |||||||||
| C340 | POP HL | |||||||||
| C341 | INC H | |||||||||
| C342 | INC D | |||||||||
| C343 | DEC C | |||||||||
| C344 | JR NZ,UpdateScreenDisplay_KeepRowDestination | |||||||||
| C346 | POP BC | Restore the screen registers from the stack. | ||||||||
| C347 | POP DE | |||||||||
| C348 | POP HL | |||||||||
| C349 | PUSH AF | And call AdvanceScreenPosition to advance the screen position. | ||||||||
| C34A | CALL AdvanceScreenPosition | |||||||||
| C34D | CALL AdvanceScreenPosition | Call AdvanceScreenPosition to advance screen position. | ||||||||
| C350 | POP AF | |||||||||
| C351 | DEC C | Jump back to UpdateScreenDisplay_Loop while the count is not finished. | ||||||||
| C352 | JR NZ,UpdateScreenDisplay_Loop | |||||||||
| C354 | CP $10 | Go to UpdateScreenDisplay_Next if it is 10. | ||||||||
| C356 | JR Z,UpdateScreenDisplay_Next | |||||||||
| C358 | LD HL,$5820 | Point at the second and first attribute rows, ready to scroll the attributes up one row. | ||||||||
| C35B | LD DE,$5800 | |||||||||
| C35E | LD BC,$0220 | Take 0220 bytes, seventeen attribute rows. | ||||||||
| C361 | LDIR | Scroll the attributes up one row. | ||||||||
| UpdateScreenDisplay_Next | C363 | LD A,($C128) | Set B to 24 and jump to UpdateScreenDisplay_FillSpaces if the screen flag at C128 is zero. | |||||||
| C366 | AND A | |||||||||
| C367 | LD B,$24 | |||||||||
| C369 | JR Z,UpdateScreenDisplay_FillSpaces | |||||||||
| C36B | LD B,$12 | Count 12. | ||||||||
| UpdateScreenDisplay_FillSpaces | C36D | LD HL,$5020 | Point HL at the screen address 5020 set C to 02 and take a space. | |||||||
| C370 | LD C,$02 | |||||||||
| C372 | LD A,$20 | |||||||||
| UpdateScreenDisplay_0 | C374 | CALL PrintCharacter | Call PrintCharacter to print a space. | |||||||
| C377 | DJNZ UpdateScreenDisplay_0 | Count the next entry and repeat from UpdateScreenDisplay_0. | ||||||||
| C379 | POP DE | Restore the saved source, the saved pointer and the saved count from the stack. | ||||||||
| C37A | POP HL | |||||||||
| C37B | POP BC | |||||||||
| C37C | RET | Return. | ||||||||
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