wincc画面中是通过文本列表进行PLC时钟设置的，列表中时钟的读、写命令与M80寄存器位1关联。使用PLCMSIM进行仿真时，在wincc画面中对PLC时钟进行读、写操作却毫无反应，请问是什么原因？
补充：
PLC编程如下：
程序段1
A M 80.1
JCN aaa
CALL "SET_CLK" //SFC0
PDT :="set_clock".DAT2 //P#DB99.DBX0.0
RET_VAL:=#WRITE
NOP 0
aaa: CALL "READ_CLK" //SFC1
RET_VAL:=#READ
CDT :="read_clock".DAT1 //P#DB100.DBX0.0


程序段2
L DB100.DBB 0
BTI
L 2000
+I
T "time".year //DB1.DBW0
L DB100.DBB 1
BTI
T "time".month //DB1.DBW2
L DB100.DBB 2
BTI
T "time".day //DB1.DBW4
L DB100.DBB 3
BTI
T "time".hour //DB1.DBW6
L DB100.DBB 4
BTI
T "time".minute //DB1.DBW8
L DB100.DBB 5
BTI
T "time".second //DB1.DBW10
L DB100.DBB 7
L 2#1111
AW
L 1
-I
T "time".week //DB1.DBW12

程序段3
L "time".yearset //DB1.DBW14
L 2000
-I
T DB99.DBB 0
L "time".monthsset //DB1.DBW16
ITB
T DB99.DBB 1
L "time".dayset //DB1.DBW18
ITB
T DB99.DBB 2
L "time".hourset //DB1.DBW20
ITB
T DB99.DBB 3
L "time".minuteset //DB1.DBW22
ITB
T DB99.DBB 4
L "time".secondset //DB1.DBW24
ITB
T DB99.DBB 5