Hitachi NJI-350B manual Syntax of SB n, RTS, INT n and RTI, 114

Chapter 5 Instruction Specifications

RTI

Syntax of SB n, RTS, INT n and RTI

1] A subroutine can be programmed between a normal scan and interrupt scan, between two interrupt scans, or after the final interrupt scan.

Program head

SB 1

Normal scanRTS Subroutine 1

END

Interrupt	Subroutine area	SB 2	Subroutine 2
	INT 1	RTS
scan	RTI	SB 10	Subroutine 10
	Subroutine area
Interrupt	INT 2	RTS
		SB 11	Subroutine 11
scan	RTI
	Subroutine area	RTS
		SB 12	Subroutine 12
	Program end
		RTS

2] Program the subroutine start (SB n) and subroutine end (RTS) instructions without specifying startup conditions.

Startup	SB n
condition
Program
Startup		• The RTS startup condition error
	RTS	will occur during operation pre-
condition
		processing.

3] Program the interrupt scan start (INT n) and scan complete (RTI) instructions without specifying startup conditions.

Startup	INT n
condition

Program

5] It is also possible to program a subroutine with multiple entry points and one exit.

			SB 1
SB 1	SB 2	SB 3	JMP 1
			SB 2
JMP 1		JMP 1
			JMP 1
			SB 3
	LBL 1
	RTS
			LBL 1
			RTS

6] It is also possible to program a interrupt scan with many entry points and one exit.

INT 0	INT 1	INT 2	INT 0
JMP 1		JMP 1	JMP 1
			INT 2
			JMP 1
			INT 1
	LBL 1
	RTI		LBL 1
			RTI

7] Nesting of subroutines is allowed up to 5 levels.

1st level 2nd level 3rd level 4th level 5th level

SB 1	SB 20
		SB 30
	CAL 30		SB 40
				SB 50
CAL 20		CAL 40	CAL 50
				RTS
		RTS	RTS
RTS	RTS

Startup

condition RT1

4] The same subroutine can be called from a normal scan, interrupt scan or subroutine.

Program head

CAL 1

Normal scan	CAL 1
	END
	SB 2
Subroutine 2 CAL 1
	RTS
Subroutine 1	SB 1
	RTS
	INI 0
Interrupt scan	CAL 1
	RTI

Program head

END

SB 20

RTS

SB 1

RTS

INT 0

RTI

SB 40

RTS

SB 30

RTS

SB 50

RTS

(1)As shown to the left, the subroutine program order and nesting order have no relationship.

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