Avalon: Routine at 57081

57081: Clear the scroll status panel at the bottom of the screen

Used by the routines at 49215, 51043, 55944, 58599, 58945, 59130 and 59956.
57081	LD HL,20551	Screen address for the top left of the scroll
57084	LD C,5	5 character rows to clear
57086	LD D,18	18 columns wide
57088	LD B,8	8 pixels in each character square
57090	LD (HL),0	Clear screen address byte
57092	INC H	Move down 1 pixel row
57093	DJNZ 57090	Repeat x 8 pixel rows
57095	LD A,H	Return address pointer to top of block
57096	SUB 8
57098	LD H,A
57099	INC L	...and move right one character square
57100	DEC D	Repeat for 18 columns
57101	JR NZ,57088
57103	LD A,L
57104	ADD A,14	Increase low byte of screen address pointer to move to next row down
57106	LD L,A
57107	DEC C	Repeat until all 5 rows are clear
57108	JR NZ,57086
57110	LD HL,20711
Finally, clear the bottom 4 pixels of the scroll, just under the dragon flame energy bar. This space doesn't seem to get text or graphics on it - and it's slightly odd that the whole line isn't cleared (only 11 columns). Perhaps the scroll status display was set out differently to begin with.
57113	LD D,11	11 character columns to clear
57115	LD B,4	Just 4 pixels (half a character square) needed to clear
57117	LD (HL),0	Clear the screen byte
57119	INC H	Move to the next pixel line down
57120	DJNZ 57117	...and repeat for the 4 pixel rows
57122	DEC H	Return back up 4 pixels...
57123	DEC H
57124	DEC H
57125	DEC H
57126	INC L	...and move right one square
57127	DEC D	Repeat x 11 columns
57128	JR NZ,57115	Repeat x 11 columns
This sets two screen graphic bytes in the top left of the smaller overlapping scroll (in the bottom right of the screen). It's unclear why this is needed - these bytes don't seem to get overwritten at any point. Again, perhaps it's from a previous clearing or graphic routine that affected them in some way.
57130	LD HL,22487	Screen address for top left of overlapping scroll
57133	LD (HL),7	First byte
57135	INC HL	First byte
57136	LD (HL),255	Second byte
57138	RET	Second byte