我想用pid来调节以下内容：给定温度，通过调节阀门的开度来使现场温度维持在给定温度。我在ob32(circle interrupt time 500ms)里调用fb41关联db20块，又在db2里定义了下面几个地址，建了一张变量表来调整、监控，可是无论我怎么调整数据输出总是为0，请各位老师给我指正，谢谢！！！
//network 1
A(
L "BT_PV" // 从现场才过来的温度瞬时值
T MD 250
SET
SAVE
CLR
A BR
)
JNB _001
L MD 250
DTR
T DB2.DBD 4
_001: NOP 0
//network 2
A(
A(
A DB2.DBX 28.0
= L 20.1
BLD 103
A(
ON DB2.DBX 28.0
O DB2.DBX 28.0
)
JNB _002
CALL "CONT_C" , DB20
COM_RST :=
MAN_ON :=L20.1
PVPER_ON:=
P_SEL :=
I_SEL :=
INT_HOLD:=
I_ITL_ON:=
D_SEL :=
CYCLE :=
SP_INT :=DB2.DBD0 //温度给定值
PV_IN :=DB2.DBD4 //温度过程值
PV_PER :=
MAN :=DB2.DBD8
GAIN :=DB2.DBD12
TI :=DB2.DBD16 //20s
TD :=DB2.DBD20 //10s
TM_LAG :=
DEADB_W :=DB2.DBD24 // 5
LMN_HLM :=2.764800e+004
LMN_LLM :=0.000000e+000
PV_FAC :=
PV_OFF :=
LMN_FAC :=
LMN_OFF :=
I_ITLVAL:=
DISV :=
LMN :=MD254 //输出经转换格式到阀门开度
LMN_PER :=
QLMN_HLM:=
QLMN_LLM:=
LMN_P :=
LMN_I :=
LMN_D :=
PV :=
ER :=
_002: A BR
)
JNB _003
L MD 254
TRUNC
T MD 258
AN OV
SAVE
CLR
_003: A BR
)
JNB _004
L MD 258
T "BZ_SV" //阀门开度
_004: NOP 0