显然，每个扫描周期都要调用两个子程序，当调用子程序0时，I0.0传到LO.0,I0.1传到LO.1,运算结果经L0.2传递到Q0.0,在调用子程序1时（假设I0.2没用闭合，I0.3没有断开），则L0.0的值保持在子程序0里的状态，Q0.2是否有输出，取决于I0.0是否闭合。显然这不是编程者的目的，为了解决这种情况，可以在子程序调用前把临时变量清零。其本质就是yanxiao说的L区的变量，先赋值，后使用。
具体这个程序，可以这样用，你试一下；
ORGANIZATION_BLOCK MAIN:OB1
TITLE=
//PROGRAM COMMENTS
//Press F1 for help and example program
//

BEGIN
NETWORK 1 //NETWORK TITLE (single line)
//
//NETWORK COMMENTS
//
LD SM0.0
= L60.0
LD I0.0
= L63.7
LDN I0.1
= L63.6
LD L60.0
CALL SBR_0 L63.7 L63.6 Q0.0

NETWORK 2
LD SM0.0
= L60.0
LD I0.2
= L63.7
LDN I0.3
= L63.6
LD L60.0
CALL SBR_1 L63.7 L63.6 Q0.1

END_ORGANIZATION_BLOCK

SUBROUTINE_BLOCK SBR_0:SBR0
TITLE=
//SUBROUTINE COMMENTS
//Press F1 for help and example program
//

VAR_INPUT
light_on:BOOL;
light_off:BOOL;
END_VAR
VAR_OUTPUT
light:BOOL;
END_VAR
BEGIN
NETWORK 1
LD SM0.0
MOVB 0 LB0

NETWORK 2 //NETWORK TITLE (single line)
//
//NETWORK COMMENTS
//
LD #light_on
O #light
A #light_off
= #light

END_SUBROUTINE_BLOCK

SUBROUTINE_BLOCK SBR_1:SBR1
TITLE=
//SUBROUTINE COMMENTS
//Press F1 for help and example program
//

VAR_INPUT
switch_on:BOOL;
switch_off:BOOL;
END_VAR
VAR_OUTPUT
light:BOOL;
END_VAR
BEGIN
NETWORK 1
LD SM0.0
MOVB 0 LB0

NETWORK 2 //NETWORK TITLE (single line)
//
//NETWORK COMMENTS
//
LD #switch_on
O #light
A #switch_off
= #light

END_SUBROUTINE_BLOCK

INTERRUPT_BLOCK INT_0:INT0
TITLE=
//INTERRUPT ROUTINE COMMENTS
//Press F1 for help and example program
//

BEGIN
NETWORK 1 //NETWORK TITLE (single line)
//
//NETWORK COMMENTS
//

END_INTERRUPT_BLOCK
把此文件保存为文本格式，改变扩展名为.awl格式，然后用FILE---import 导入
，下载到PLC中，试试看，结果怎样？