Elmo HARmonica Usrsubj jump To User Subroutine, Usrsubrt Return from user subroutine, OP2

HARSFEN0602ElmoHARmonicaSoftwareManual PRELIMINARYDRAFT

7.7.39USRSUBJ – jump To User Subroutine

Purpose:

Call to user subroutine (push relevant function data to stack).

	SEE 8.2
	Algorithm:
	BP	(SP)		(save base pointer)
	SP	SP + 1
	OP2	(SP)		(save return address)
	SP	SP + 1
	FuncIndex		(SP)			(save function index)
	SP →SP + 1
	NArgIn (SP)					(save number of input arguments)
7.7.39.1.1.1.1.1					SP		SP + 1
	NActArgOut			(SP)		(save number of actual output arguments)
	SP	SP + 1
	SP	BP		(update base pointer)
	PC →→FuncAddr→					(jump to user subroutine)
	Attributes
	Attribute							Value	Comment
		→
	Op code					→			May change in future
									versions
	Number of arguments							2
			→
	Argument type1							Unsigned short integer	Lower 8 bits :
									Actual ouput arguments
									Upper 8 bits :
									Subroutine Index
	Argument type1							Unsigned short integer	Return Address
	Addressing mode1							Immediate2
	Addressing mode1							Immediate2
	Promotion							N.A.
	Output type							N.A.
	Imposes end of line							Yes	jump address is out of the
									present executing line.

92

7.7.40USRSUBRT – Return from user subroutine

Purpose:

Return from user subroutine - restore stack to its state before function call, save output arguments in stack and jump to return address.

See 8.2

Algorithm:

7.7.40.1.1.1.1.1(SP-1) nActArgOut (number of actual output arguments)

(SP-2)	nArgIn (num of input arguments)
(SP-4)	RtAddr (return address)
SP	BP – 5 - nArgIn
(save output arguments from subroutine)
(SP-5)	BP (base pointer)
PC →RtAddr→		(return from→user subroutine)