OUT	(+FE),A	Perform the OUT operation;
				leaving the border unchanged.
		LD	B,H	Reset the B register.
		LD	C,A	Save the A register.
		BIT	4,A	Jump if at the half-cycle
		JR	NZ,03F2,BE-AGAIN	point.

After a full cycle the DE register pair is tested.

		LD	A,D	Jump forward if the last
		OR	E	complete pass has been
		JR	Z,03D6,BE-END	made already.
		LD	A,C	Fetch the saved value.
		LD	C,L	Reset the C register.
		DEC	DE	Decrease the pass counter.
		JP	(IX)	Jump back to the required
				starting location of the loop.

The parameters for the second half-cycle are set up.

03F2	BE-AGAIN	LD	C,L	Reset the C register.
		INC	C	Add '16' T states as this path 
				is shorter.
		JP	(IX)	Jump back.

Upon completion of the 'beep' the maskable interrupt has to be enabled. 

03F6	BE-END	EI		Enable interrupt.
		RET		Finally return.

THE 'BEEP' COMMAND ROUTINE
The subroutine is entered with two numbers on the calculator stack.  The topmost
number represents the 'pitch' of the note and the number underneath it represents the 'duration'.

03F8	BEEP	RST	0028,FP-CALC	The floating-point calculator is 
				used to manipulate the two values - t & P.
		DEFB	+31,duplicate	t,P,P
		DEFB	+27,int	t,P,P
		DEFB	+C0,st-mem-0	t,P,i (mem-0 holds i)
		DEFB	+03,substract	t,P (where p is the fractional
				part of P)
		DEFB	+34,stk-data	Stack the decimal value 'K'.
		DEFB	+EC,exponent+7C	0.0577622606 (which is a
		DEFB	+6C,+98,+1F,+F5	little below 12*(2^0.5)-1)
		DEFB	+04,multiply	t,pK
		DEFB	+A1,stk-one	t,pK,1
		DEFB	+0F,addition	t,pK+1
		DEFB	+38,end-calc

Now perform several tests on I, the integer part of the 'pitch'.

		LD	HL,+5C92	This is 'mem-0-1st (MEMBOT).
		LD	A,(HL)	Fetch the exponent of i.
		AND	A	Give an error if i is not in the 
		JR	NZ,046C,REPORT-B	integral (short) form.
		INC	HL	Copy the sign byte to the
		LD	C,(HL)	C register.
		INC	HL	Copy the low-byte to the
		LD	A,B	register.
		RLA		Again give report B if i does not
		SBC	A,A	satisfy the test:
		CP	C	-128<=i<=+127
		JR	NZ,046C,REPORT-B
		INC	HL
		CP	(HL)