edgeload

edge loading:
based on "The Complete SPECTRUM ROM DISASSEMBLY" by Logan & O'Hara

0x05e7	LD-EDGE-1
	7+21*(4+12)+(4+7)+4=358T
0x05ed	LD-SAMPLE
	INC B			4T
	RET Z			11/5T
	LD A,7F			7T
	IN A,FE			11T
	RRA				4T
	RET NC			11/5T
	XOR C			4T
	AND 20			7T
	JR Z,LD-SAMPLE	12/7T
	LD A,C			4T
	CPL				4T
	LD C,A			4T
	AND 7			7T
	OR 8			7T
	OUT FE,A		11T
	SCF				4T
	RET				10T

0x04d8	SA-LEADER
	DJNZ SA-LEADER	(B-1)*13+8T
	OUT FE,A		11T
	XOR 0F			7T
	LD B,A4			7T
	DEC L			4T
	JR NZ,SA-LEADER	12/7T
	DEC B			4T
	DEC H			4T
	JP P,SA-LEADER	10T
	LD B,2F			7T
0x04ea	SA-SYNC-1
	DJNZ SA-SYNC-1	(B-1)*13+8T
	OUT FE,A		11T
	LD A,0D			7T
	LD B,37			7T
0x04f2	SA-SYNC-2
	DJNZ SA-SYNC-2	(B-1)*13+8T
	OUT FE,A		11T
	LD BC,3B0E		10T
	EX AF,AF'		4T
	LD L,A			4T
	JP SA-START		10T // SA-START = 0x0507

0x0511	SA-BIT-2
	LD A,C			4T
	BIT 7,B			8T
0x0514	SA-BIT-1
	DJNZ SA-BIT-1	(B-1)*13+8T
	JR NC,SA-OUT	12/7T
	LD B,42			7T
0x051A	SA-SET
	DJNZ SA-SET		(B-1)*13+8T
0x051C	SA-OUT
	OUT FE,A		11T
	LD B,3E			7T
	JR NZ,SA-BIT-2	12/7T
	DEC B			4T
	XOR A			4T
	INC A			4T
0x0525	SA-8-BITS