Sherlock: Routine at F514

F514: Attribute Up

Used by the routine at Drawing. Moves the attribute address one row up. The attribute file begins at 5800 so a high byte of 57 means the step left the screen.
AttributeUp	F514	PUSH AF	Keep the colour and the pen, and step the screen pointer back one attribute row.
	F515	PUSH DE
	F516	LD DE,$0020
	F519	AND A
	F51A	SBC HL,DE
	F51C	LD A,H	Jump ahead to AttributeUp_Next if the high byte of the address is not 57.
	F51D	CP $57
	F51F	JR NZ,AttributeUp_Next
	F521	ADD HL,DE	Undo the step that passed the top row.
AttributeUp_Next	F522	POP DE	Restore the colour from the stack.
	F523	POP AF	Restore the colour from the stack.
	F524	RET	Return.
View the equivalent code in; The Hobbit