首先將需要讀取的PLC內部元件的地址找到，主要內部元件地址如下：
D: PLC-Address*2+1000H;
T: PLC-Address+00C0H;
C: PLC-Address*2+01C0H;
S: PLC-Address*3;
M: PLC-Address*2+0100H;
Y: PLC-Address+00A0H;
X: PLC-Address+0080H;(只能讀不能寫，輸入寄存器必須由外部信號驅動)
PLC-Address元件是指最低位開始後的第N個元件的位置。
一、VC與PLC的串口通訊主要操作：
1、對位元件和字元件狀態讀操作；
操作對象元件：PLC內部的X、Y、M、S、T、C、D元件
命令通用格式： STX CMD0 ADD LEN EXT CHK
意義： 起始符 讀命令 元件起始位 個數 停止符 校驗碼
數字代碼格式： 0X02 0X30 …… …… 0X03 ……
0x30是讀操作指令；
ADD是讀位元件或字元件的4位起始地址，高位先發，低位後發，以ASCII碼的格式發送；
LEN是一次讀取位元件或字元件的個數，最多可以讀取0xff個字節的元件，也是以ASCII碼的形式發送；
CHK是兩位和校驗，將CMD0,ADD,LEN,EXT三項進行和累計，將和累計的最低兩位轉化成ASCII，高位先發，低位後發。
在發完上述命令格式代碼後，就可以直接讀取PLC響應返回的信息，
響應信息格式：STX DATA EXT CHK
意義： 起始符 接收的數據 停止符 校驗碼
數字代碼格式：0x02 …… 0x03 ……
DATA爲我們需要讀取的數據；
需要注意的是：讀取DATA數據時遵循低位先發，高位後發的原則，所以我們解析數據的時候需要注意高低位的轉換。
CHK則爲DATA，EXT兩項的和累計的最後兩位轉化爲ASCII。
2、位元件和字元件狀態寫操作；
操作對象元件：PLC內部的XYMSTCU元件
命令通用格式：STX CMD1 ADD LEN DATA EXT CHK
意義： 起始符 讀命令 元件起始位 個數 寫入的數據 停止符 校驗碼
數字代碼格式：0X02 0X31 …… 0X03 ……
0x031是寫操作指令；
DATA是待寫入PLC緩衝區的數據，低位先發，高位後發，以ASCII碼的形式發送；
其他和讀指令一樣，此處不再重複；
發送後返回值爲06，表示寫入成功；
返回值爲15，表示寫入失敗；
數據通訊舉例：
例1：讀D0的值
D0的內部地址爲1000H=31H 30H 30H 30H
LEN表示我們需要讀字節的個數，0-7爲一個字節，D0佔兩個字節，所以LEN=30H 32H.
計算CHK校驗碼=CMD0+ADD+LEN+EXT
=30H+31H+30H+31H+30H+30H+32H+03H=157H
所以校驗碼爲35H 37H.
得到完整的數字命令格式爲：02H 30H 31H 30H 30H 30H 30H 32H 03H 35H 37H
將這段數字代碼發送給PLC，
返回代碼：02H 30H 30H 30H 30H 03H 43H 33H
得到數據段DATA爲30H,31H,30H,30H=0001B（低位先發，高位後發）=1D
至此得到D0=1.
完成IPC讀取PLC內部數據的全部過程。
IO通訊舉例：
例2：讀取Y1的值
Y1的內部地址是00A0=30H 30H 41H 30H，表示的意思是Y7-Y0的地址，Y1只是其中的一個位。
LEN因爲00A0只有一個字節，所以可以去LEN=01D=30H 31H;
計算CHK校驗碼=36H 35H;
得到完成的數字代碼爲：02H 30H 30H 30H 41H 30H 30H 31H 03H 36H 35H;
返回代碼：02H 30H 32H 03H 36H 35H
數據段爲：30H 32H=02D=0010B
從Y7-Y0低往高排列可以知，Y1現在是狀態值爲1；
如果這裏取LEN=2D=30H 32H
發送代碼：02H 30H 30H 30H 41H 30H 30H 32H 03H 36H 36H;
返回代碼：02H 30H 32H 30H 30H 03H 43H 35H
數據段爲：30H 32H 30H 30H=0002B(低位先發，高位後發)=2D
從Y7-Y0低往高排列可以知，Y1現在是狀態值爲1；
注意：全部過程中，PLC內部程序不需要做任何程序編寫。
三、PLC讀取IPC數據時：
數據通訊舉例：
例1：PLC讀取IPC內部參數X的值。
思路：1、先將X的值轉化成數字代碼形式。
2、再講X的值發送寫入PLC內部數據寄存器中；
3、然後PLC直接讀取這個數據寄存器的數據。
設：X=2;數據寫入PLC內部數據寄存器D0中
則DATA=X=2=0010H=31H 30H 30H 30H（低位先發，高位後發）;
ADD=31H 30H 30H 30H;
LEN=02D=30H 32H.;（D爲10進制；H爲16進制）
CHK=CMD1+ADD+LEN+DATA+EXT；
=31H+31H+30H+30H+30H+30H+32H+31H+30H+30H+30H+03H=218H
則校驗碼爲：31H 38H
完整的數字代碼爲：02H 31H 31H 30H 30H 30H 30H 32H 31H 30H 30H 30H 03H 31H 38H
返回值爲06表示寫入成功，PLC直接讀取D0裏面的數據即可。
完成PLC讀取IPC數據。
當然這只是即時的讀取，如果需要可控性的話，需要增加自定義讀取和發送標誌位，多加個數據用來表示控制字節用。
IO通訊舉例：
例2：IPC置位PLC內部位元件Y1
思路：1、確定Y1地址（讀操作已說明）；
2、就於寫入的原理，需要先讀取00A0的值；
3、將讀取的值與0010進行&運算，確定Y1是否爲0；
4、爲0，則將讀取值與0010進行或運算，再將得到的值轉爲數字代碼形式發送給PLC； 爲1，則表示內部Y1已經爲1，不需要重複置位；
5、寫入成功後返回06；
編寫VC程序時需要用到以上思路；
這裏我們假設我們只是寫入Y1=1來操作：
Y1的PLC內部地址爲：00A0H；表示Y7-Y0的地址，Y1只是其中一個位；
LEN取2個字節16位=30H 32H;
寫入數據：00A0表示的是Y7-Y0 8個位，需要Y1爲1，寫入00000010B=02H,但是LEN爲2，表示2個字節，所以需要寫入0002H轉化爲30H 32H 30H 30H(低位先發，高位後發)；
完整代碼：02H 31H 30H 30H 41H 30H 30H 32H 30H 32H 30H 30H 03H 32H 39H
返回：06寫入成功。
四、數據通訊VC代碼編寫分析實例：
例1：將IPC端3個數據：
X=1003.5；Y=-4500；Z=-3.1456
寫入PLC中
代碼編寫步驟：
1、將XYZ分別轉化成整數，然後保存其小數位數，這裏將XYZ分別都乘以10的N次方，直到其不在 -32767-32767範圍後分別保存乘以10的個數在N1，N2，N3中；
從而得到 X=10035 ; N1=1;
Y=-4500; N2=0;
Z=31456; N3=4;
2、將X、Y、Z、N1、N2、N3分別轉換成16進制；
3、再轉化爲16進制ASCII碼；
4、將得到的16進制ASCII碼按照X、N1、Y、N2、Z、N3的順序排列進counts[35]數組中；
5、計算校驗碼;
6、將數據counts[35]每個數轉化爲對應的兩個ASCII碼值保存於counts_ascii[70]中；
例如：“35”轉化爲“3”和“5”；
7、將ASCII碼轉化爲字符串代碼保存於a2[70],累加排列輸出；
例如：“3”的字符串代碼爲48+3=51；
8、返回值06，表示寫入成功。
例2：讀取PLC內部數據X、Y、Z的值
（讀取D0-D5的數據）
代碼編寫步驟：(思路與上例一樣)
1、將固定讀取的數字代碼發送給PLC，
固定讀取D0-D5的數字代碼爲：02H 30H 31H 30H 30H 30H 30H 43H 03H 36H 37H
2、發送成功後，則有數據信息反饋；不成功則返回15；
3、將返回的窗口輸出字符串依次保存在字符串數組char s1[84]中；
4、將數組s1轉化爲數字保存在數據b中；類似：字符串數字51=“3”；
5、將數組b轉爲16進制ASCII，再轉化爲10進制保存在數組c中；
例如：“3”“5”=3*10+5=35；再如：35H=5D；
6、將數組c轉爲2進制，方便判斷正負數和後期運算，保存在數值c2中；
7、判斷正負數，設立標誌位flog；
如果爲負數，則將其二進制取反加1後轉化爲10進制整數；
如果不爲負數，則直接轉化爲10進制整數；
8、得到的數分別保存在D0、D1、D2、D3、D4、D5中（IPC內部變量區別開PLC內部數據寄存器）；
自定義運算；
可以得到 X=D0/(10^D1);//D0除以10的D1次方
Y=D2/(10^D3);
Z=D4/(10^D5);
'Private Declare Sub Sleep Lib "kernel32" (ByVal dwseconds As Long) '延時函數毫秒
Dim ik As Integer
Dim str_write() As Byte '發送數組
Dim str_val(0 To 5) As Byte
Dim 非讀操作 As Boolean '此位爲真是表示有非讀命令等待執行，那麼暫停讀命令，執行非讀操作
Dim 何種非讀操作 As Integer '此變量用來區分等待的是何種非讀命令
Dim 讀操作 As Boolean '此變量作用：當有非讀命令而讀操作的接收處理沒有完成時，先完成讀命令的接收處理
Dim i As Integer '此變量作用：讀操作時因爲讀的類型不一樣，所以每次讀一種（如X），然後下一次根據i的數值判斷是應該讀那種類型。
Dim 第一次 As Boolean
Dim dz As Integer '元件操作地址
Dim lie As Byte, lie1 As Byte, lie2 As Byte '元件操作類型
Dim SRet As Byte
Private Sub Command1_Click(Index As Integer) '寫VW0---VW30
Dim shuju As String
Dim shuju1 As String
Dim shuju2 As String
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非讀操作 = True
何種非讀操作 = 3
shuju = Right("0000" + Hex(Text4(Index).Text), 4)
shuju1 = ("&H" & Mid(shuju, 1, 2))
shuju2 = ("&H" & Mid(shuju, 3, 2))
ReDim str_write(0 To 38) As Byte '重新定義數組
str_write(0) = &H68
str_write(1) = &H21
str_write(2) = &H21
str_write(3) = &H68
str_write(4) = &H2
str_write(5) = &H0
str_write(6) = &H6C
str_write(7) = &H32
str_write(8) = &H1
str_write(9) = &H0
str_write(10) = &H0
str_write(11) = &H0
str_write(12) = &H0
str_write(13) = &H0
str_write(14) = &HE
str_write(15) = &H0
str_write(16) = &H6
str_write(17) = &H5 '寫
str_write(18) = &H1
str_write(19) = &H12
str_write(20) = &HA
str_write(21) = &H10
str_write(22) = &H2
str_write(23) = &H0
str_write(24) = &H2
str_write(25) = &H0
str_write(26) = &H1
str_write(27) = &H84
str_write(28) = &H0
str_write(29) = &H0
str_write(30) = (Index * 2 * 8) Mod 256
str_write(31) = &H0
str_write(32) = &H4
str_write(33) = &H0
str_write(34) = &H10
str_write(35) = shuju1
str_write(36) = shuju2
str_write(37) = SumChk(str_write)
str_write(38) = &H16
End Sub
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Private Sub Command2_Click(Index As Integer) 'S元件狀態操作
非讀操作 = True
何種非讀操作 = 0
dz = Index
lie = &H4
lie1 = &H0
lie2 = &H7C
If Command2(Index).Caption = "S0." + Trim(Index) + "復位" Then
SRet = &H0
Else
SRet = &H1
End If
End Sub
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Private Sub Command3_Click(Index As Integer) 'M元件狀態操作
非讀操作 = True
何種非讀操作 = 0
dz = Index
lie = &H83
lie1 = &H0
lie2 = &H7C
If Command3(Index).Caption = "M0." + Trim(Index) + "復位" Then
SRet = &H0
Else
SRet = &H1
End If
End Sub
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Private Sub Command4_Click(Index As Integer) 'V元件狀態操作
非讀操作 = True
何種非讀操作 = 0
dz = Index
lie = &H84
lie1 = &H1
lie2 = &H6C
If Command4(Index).Caption = "V0." + Trim(Index) + "復位" Then
SRet = &H0
Else
SRet = &H1
End If
End Sub
Private Sub Command5_Click() '啓動
非讀操作 = True
何種非讀操作 = 1
ReDim str_write(0 To 38) As Byte '重新定義數組
str_write(0) = &H68
str_write(1) = &H21
str_write(2) = &H21
str_write(3) = &H68
str_write(4) = &H2
str_write(5) = &H0
str_write(6) = &H7C
str_write(7) = &H32
str_write(8) = &H1
str_write(9) = &H0
str_write(10) = &H0
str_write(11) = &H0
str_write(12) = &H0
str_write(13) = &H0
str_write(14) = &H14
str_write(15) = &H0
str_write(16) = &H0
str_write(17) = &H28
str_write(18) = &H0
str_write(19) = &H0
str_write(20) = &H0
str_write(21) = &H0
str_write(22) = &H0
str_write(23) = &H0
str_write(24) = &HFD
str_write(25) = &H0
str_write(26) = &H0
str_write(27) = &H9
str_write(28) = &H50
str_write(29) = &H5F
str_write(30) = &H50
str_write(31) = &H52
str_write(32) = &H4F
str_write(33) = &H47
str_write(34) = &H52
str_write(35) = &H41
str_write(36) = &H4D
str_write(37) = SumChk(str_write)
str_write(38) = &H16
End Sub
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Private Sub Command6_Click() '停止
ReDim str_write(0 To 34) As Byte '重新定義數組
非讀操作 = True
何種非讀操作 = 2
str_write(0) = &H68
str_write(1) = &H1D
str_write(2) = &H1D
str_write(3) = &H68
str_write(4) = &H2
str_write(5) = &H0
str_write(6) = &H7C
str_write(7) = &H32
str_write(8) = &H1
str_write(9) = &H0
str_write(10) = &H0
str_write(11) = &H0
str_write(12) = &H0
str_write(13) = &H0
str_write(14) = &H10
str_write(15) = &H0
str_write(16) = &H0
str_write(17) = &H29
str_write(18) = &H0
str_write(19) = &H0
str_write(20) = &H0
str_write(21) = &H0
str_write(22) = &H0
str_write(23) = &H9
str_write(24) = &H50
str_write(25) = &H5F
str_write(26) = &H50
str_write(27) = &H52
str_write(28) = &H4F
str_write(29) = &H47
str_write(30) = &H52
str_write(31) = &H41
str_write(32) = &H4D
str_write(33) = SumChk(str_write)
str_write(34) = &H16
End Sub
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Private Sub Combo1_Click() '通訊口選擇
Call CommSet '調用通訊口設置過程
End Sub
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Private Sub CommSet()
On Error GoTo err1 '此處作用：如果您選擇了電腦中不存在的通訊口，則提示“無效的通訊口”
If MSComm1.PortOpen = True Then MSComm1.PortOpen = False
MSComm1.CommPort = Val(Mid(Combo1.Text, 4, 1))
MSComm1.Settings = "9600,e,8,1"
MSComm1.InBufferCount = 0
MSComm1.OutBufferCount = 0
MSComm1.InputLen = 0
MSComm1.RThreshold = 0
MSComm1.InputMode = comInputModeBinary
MSComm1.PortOpen = True
第一次 = False
非讀操作 = False
str_val(0) = &H10
str_val(1) = &H2
str_val(2) = &H0
str_val(3) = &H5C
str_val(4) = &H5E
str_val(5) = &H16
Timer1.Enabled = True
Exit Sub
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err1:
MsgBox Err.Description '錯誤提示
End Sub
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Private Sub Form_Load()
Dim g As Integer
On Error GoTo err1 '此處作用：如果您選擇了電腦中不存在的通訊口，則提示“無效的通訊口”
For g = 1 To 9 '添加通訊選擇
Combo1.AddItem "Com" & Trim$(Str$(g))
Next g
MSComm1.CommPort = 1
MSComm1.Settings = "9600,e,8,1"
MSComm1.InBufferCount = 0
MSComm1.OutBufferCount = 0
MSComm1.InputLen = 0
MSComm1.RThreshold = 0
MSComm1.InputMode = comInputModeBinary
MSComm1.PortOpen = True
第一次 = False
非讀操作 = False
str_val(0) = &H10
str_val(1) = &H2
str_val(2) = &H0
str_val(3) = &H5C
str_val(4) = &H5E
str_val(5) = &H16
Timer1.Enabled = True
Exit Sub
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err1:
MsgBox Err.Description '錯誤提示
End Sub
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Private Sub Form_Unload(Cancel As Integer)
MSComm1.InBufferCount = 0
MSComm1.OutBufferCount = 0
If MSComm1.PortOpen = True Then MSComm1.PortOpen = False
End
End Sub
Private Function SumChk(Dats) As Byte '校驗和計算
Dim l As Integer, j As Integer
Dim Temp_FCS As Variant
l = UBound(Dats)
For j = 4 To l 'Len 函數，返回 Long，其中包含字符串內字符的數目，或是存儲一變量所需的字節數
Temp_FCS = Temp_FCS + str_write(j)
Next j
SumChk = Temp_FCS Mod 256
End Function
Private Function dec2bin(Dats$) As String '轉換成二進制
Dim bin8
Dim bin4
Dim bin2
Dim bin1
Dim bin16
Dim bin32
Dim bin64
Dim bin128
If Dats \ 128 >= 1 Then
bin128 = 1
Else
bin128 = 0
End If
If (Dats Mod 128) \ 64 >= 1 Then
bin64 = 1
Else
bin64 = 0
End If
If (Dats Mod 64) \ 32 >= 1 Then 'Mod用來對兩個數作除法並且只返回餘數
bin32 = 1
Else
bin32 = 0
End If
If (Dats Mod 32) \ 16 >= 1 Then
bin16 = 1
Else
bin16 = 0
End If
If (Dats Mod 16) \ 8 >= 1 Then '\ 運算符用來對兩個數作除法並返回一個整數
bin8 = 1
Else
bin8 = 0
End If
If (Dats Mod 8) \ 4 >= 1 Then 'Mod用來對兩個數作除法並且只返回餘數
bin4 = 1
Else
bin4 = 0
End If
If (Dats Mod 4) \ 2 >= 1 Then
bin2 = 1
Else
bin2 = 0
End If
If Dats Mod 2 = 0 Then
bin1 = 0
Else
bin1 = 1
End If
bin128 = CStr(bin128) 'CStr 函數將一數值轉換爲 String
bin64 = CStr(bin64)
bin32 = CStr(bin32)
bin16 = CStr(bin16)
bin8 = CStr(bin8) 'CStr 函數將一數值轉換爲 String
bin4 = CStr(bin4)
bin2 = CStr(bin2)
bin1 = CStr(bin1)
dec2bin = bin128 + bin64 + bin32 + bin16 + bin8 + bin4 + bin2 + bin1
End Function
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Private Sub MSComm1_OnComm()
Dim rcv_array() As Byte
Dim rcv_len As Long
Dim read As String, read1 As String
Dim j As Integer
Dim wei(2) As String
If MSComm1.CommEvent = comEvReceive Then 'CommEvent的屬性返回的值爲comEvReceive時是發生了接收事件.
rcv_array = MSComm1.Input
If 第一次 = True Then '判斷髮送的是那一組
If Right("00" + Hex(rcv_array(0)), 2) <> "E5" Then '如果返回的不是E5，則重新發數據
Shape6.BackColor = &HC0&
MSComm1.RThreshold = 0
Timer1.Enabled = True
Timer2.Enabled = False
Text5 = "1"
Else '如果是E5，則發最後一組數據
If 非讀操作 = True And 讀操作 = False Then '如果是非讀命令產生的接收事件
Select Case 何種非讀操作
Case 0 '置/復位
MSComm1.RThreshold = 24
Case 1 'PLC啓動
MSComm1.RThreshold = 20
Case 2 'PLC停止
MSComm1.RThreshold = 20
Case 3 '數值寫入
MSComm1.RThreshold = 18
End Select
Else '如果是實時監控
Select Case i
Case 0 '讀M0.0—M0.7
MSComm1.RThreshold = 28
Case 1 '讀T0
MSComm1.RThreshold = 30
Case 2 '讀V0.0—V0.7
MSComm1.RThreshold = 28
Case 3 '讀輸入
MSComm1.RThreshold = 29
Case 4 '讀VW0—VW15
MSComm1.RThreshold = 59
Case 5 '讀輸出
MSComm1.RThreshold = 29
Case 6 '讀S0.0—S0.7
MSComm1.RThreshold = 28
Case 7 '讀C0
MSComm1.RThreshold = 30
End Select
End If '判斷非讀操作結束
MSComm1.InBufferCount = 0
MSComm1.OutBufferCount = 0
MSComm1.Output = str_val '發送命令
第一次 = False
Text5 = "2"
End If '判斷返回的E5是否正確結束
Else '如果是第二組命令
rcv_len = UBound(rcv_array) '返回一個 Long 型數據，其值爲指定的數維組可用的最大下標
For j = 0 To rcv_len
read = read & Right("00" + Hex(rcv_array(j)), 2)
Next j
If 非讀操作 = True And 讀操作 = False Then '如果是非讀命令產生的接收事件
非讀操作 = False '
Shape6.BackColor = &HC0&
MSComm1.InBufferCount = 0
MSComm1.OutBufferCount = 0
Timer1.Enabled = True
Else '如果是實時監控命令產生的接收事件
Select Case i
Case 0 '讀M0.0—M0.7
read1 = Val("&H" + Mid(Right(read, 6), 1, 2))
wei(0) = dec2bin(read1) '調用十二進轉二進制過程
For j = 0 To 7
If Mid(wei(0), 8 - j, 1) = "1" Then
Shape4(j).BackColor = &HC0&
Command3(j).Caption = "M0." + Trim(j) + "復位"
Else
Shape4(j).BackColor = &HE0E0E0
Command3(j).Caption = "M0." + Trim(j) + "置位"
End If
Next j
Case 1 '讀T0
read1 = Val("&H" + Mid(Right(read, 8), 1, 4))
Text2.Text = read1 'T當前值顯示
Case 2 '讀V0.0—V0.7
read1 = Val("&H" + Mid(Right(read, 6), 1, 2))
wei(0) = dec2bin(read1) '調用十二進轉二進制過程
For j = 0 To 7
If Mid(wei(0), 8 - j, 1) = "1" Then
Shape5(j).BackColor = &HC0&
Command4(j).Caption = "V0." + Trim(j) + "復位"
Else
Shape5(j).BackColor = &HE0E0E0
Command4(j).Caption = "V0." + Trim(j) + "置位"
End If
Next j
Case 3 '讀輸入
read1 = Mid(Right(read, 8), 1, 4)
wei(0) = dec2bin(Val("&H" + Mid(read1, 1, 2))) '調用十二進轉二進制過程
wei(1) = dec2bin(Val("&H" + Right(read1, 2))) '調用十二進轉二進制過程
wei(2) = wei(1) + wei(0)
For j = 0 To 15
If Mid(wei(2), 16 - j, 1) = "1" Then
Shape1(j).BackColor = &HC0&
Else
Shape1(j).BackColor = &HE0E0E0
End If
Next j
Case 4 '讀VW0—VW15
read1 = Mid(Right(read, 68), 1, 64)
For j = 0 To 15
Text1(j).Text = Val("&H" + Mid(read1, 1 + j * 4, 4))
Next j
Case 5 '讀輸出
read1 = Mid(Right(read, 8), 1, 4)
wei(0) = dec2bin(Val("&H" + Mid(read1, 1, 2))) '調用十二進轉二進制過程
wei(1) = dec2bin(Val("&H" + Right(read1, 2))) '調用十二進轉二進制過程
wei(2) = wei(1) + wei(0)
For j = 0 To 15
If Mid(wei(2), 16 - j, 1) = "1" Then
Shape2(j).BackColor = &HC0&
Else
Shape2(j).BackColor = &HE0E0E0
End If
Next j
Case 6 '讀S0.0—S0.7
read1 = Val("&H" + Mid(Right(read, 6), 1, 2))
wei(0) = dec2bin(read1) '調用十二進轉二進制過程
For j = 0 To 7
If Mid(wei(0), 8 - j, 1) = "1" Then
Shape3(j).BackColor = &HC0&
Command2(j).Caption = "S0." + Trim(j) + "復位"
Else
Shape3(j).BackColor = &HE0E0E0
Command2(j).Caption = "S0." + Trim(j) + "置位"
End If
Next j
Case 7 '讀C0
read1 = Val("&H" + Mid(Right(read, 8), 1, 4))
Text3.Text = read1 'C當前值顯示
i = -1 '常規讀取全部完成，從頭開始，因爲下面有一個+1命令，所以此處賦-1
End Select
i = i + 1 '進行下一個類型的常規讀取
讀操作 = False '讀操作接收處理完成
Shape6.BackColor = &HC0&
Timer1.Enabled = True '進行下一個類型的常規讀取
Timer2.Enabled = False
End If
End If '判斷第一組發送命令結束
End If
End Sub
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Private Sub Timer1_Timer()
第一次 = True
MSComm1.RThreshold = 1 '因爲PLC接收到寫或是置位命令，只返回一個字符，所以設爲1（RThreshold：定義接收緩衝區接收多少個字符後產生COMMFX_OnComm事件）
If 非讀操作 = True Then '如果有非讀命令存在
Select Case 何種非讀操作
Case 0
ReDim str_write(0 To 37) As Byte '重新定義數組
str_write(0) = &H68
str_write(1) = &H20
str_write(2) = &H20
str_write(3) = &H68
str_write(4) = &H2
str_write(5) = &H0
str_write(6) = lie2 '類型
str_write(7) = &H32
str_write(8) = &H1
str_write(9) = &H0
str_write(10) = &H0
str_write(11) = &H0
str_write(12) = &H0
str_write(13) = &H0
str_write(14) = &HE
str_write(15) = &H0
str_write(16) = &H5
str_write(17) = &H5
str_write(18) = &H1
str_write(19) = &H12
str_write(20) = &HA
str_write(21) = &H10
str_write(22) = &H1
str_write(23) = &H0
str_write(24) = &H1
str_write(25) = &H0
str_write(26) = lie1 '存儲器類型，01：V存儲器 00：其它
str_write(27) = lie '讀不同元件的代碼
str_write(28) = &H0
str_write(29) = &H0
str_write(30) = dz
str_write(31) = &H0
str_write(32) = &H3
str_write(33) = &H0
str_write(34) = &H1
str_write(35) = SRet '置/復位
str_write(36) = SumChk(str_write)
str_write(37) = &H16
End Select
Else ' 如果沒有非讀命令則執行常規輪詢
讀操作 = True '置真的目的：當有非讀命令而讀操作的接收處理沒有完成時，先完成讀命令的接收處理
Select Case i
Case 0 '讀M0.0—M0.7
ReDim str_write(0 To 32) As Byte '重新定義數組
str_write(0) = &H68
str_write(1) = &H1B
str_write(2) = &H1B
str_write(3) = &H68
str_write(4) = &H2
str_write(5) = &H0
str_write(6) = &H6C
str_write(7) = &H32
str_write(8) = &H1
str_write(9) = &H0
str_write(10) = &H0
str_write(11) = &H0
str_write(12) = &H0
str_write(13) = &H0
str_write(14) = &HE
str_write(15) = &H0
str_write(16) = &H0
str_write(17) = &H4 '讀
str_write(18) = &H1
str_write(19) = &H12
str_write(20) = &HA
str_write(21) = &H10
str_write(22) = &H2 '讀取位，字節，字，雙字（1，2，4，8）
str_write(23) = &H0
str_write(24) = &H1 '以字節爲單位，連續讀取的字節數
str_write(25) = &H0
str_write(26) = &H0 '存儲器類型，01：V存儲器 00：其它
str_write(27) = &H83 '讀不同元件的代碼
str_write(28) = &H0
str_write(29) = &H0 '高位地址 地址轉換地16進制 （字節號*8+位號）\256
str_write(30) = &H0 '低位地址 地址轉換地16進制 （字節號*8+位號）Mod 256
str_write(31) = SumChk(str_write)
str_write(32) = &H16
Case 1 '讀T0
ReDim str_write(0 To 32) As Byte '重新定義數組
str_write(0) = &H68
str_write(1) = &H1B
str_write(2) = &H1B
str_write(3) = &H68
str_write(4) = &H2
str_write(5) = &H0
str_write(6) = &H7C
str_write(7) = &H32
str_write(8) = &H1
str_write(9) = &H0
str_write(10) = &H0
str_write(11) = &H0
str_write(12) = &H8 '&H8
str_write(13) = &H0
str_write(14) = &HE
str_write(15) = &H0
str_write(16) = &H0
str_write(17) = &H4 '讀
str_write(18) = &H1
str_write(19) = &H12
str_write(20) = &HA
str_write(21) = &H10
str_write(22) = &H1F '讀取位，字節，字，雙字（1，2，4，8）
str_write(23) = &H0
str_write(24) = &H1 '讀取數據個數
str_write(25) = &H0
str_write(26) = &H0 '存儲器類型，01：V存儲器 00：其它
str_write(27) = &H1F '讀不同元件的代碼
str_write(28) = &H0
str_write(29) = &H0 '高位地址 地址轉換地16進制 （字節號*8+位號）\256
str_write(30) = &H0 '低位地址 地址轉換地16進制 （字節號*8+位號）Mod 256
str_write(31) = SumChk(str_write)
str_write(32) = &H16
Case 2 '讀V0.0—V0.7
ReDim str_write(0 To 32) As Byte '重新定義數組
str_write(0) = &H68
str_write(1) = &H1B
str_write(2) = &H1B
str_write(3) = &H68
str_write(4) = &H2
str_write(5) = &H0
str_write(6) = &H6C
str_write(7) = &H32
str_write(8) = &H1
str_write(9) = &H0
str_write(10) = &H0
str_write(11) = &H0
str_write(12) = &H0
str_write(13) = &H0
str_write(14) = &HE
str_write(15) = &H0
str_write(16) = &H0
str_write(17) = &H4 '讀
str_write(18) = &H1
str_write(19) = &H12
str_write(20) = &HA
str_write(21) = &H10
str_write(22) = &H2 '讀取位，字節，字，雙字（1，2，4，8）
str_write(23) = &H0
str_write(24) = &H1 '讀取數據個數
str_write(25) = &H0
str_write(26) = &H1 '存儲器類型，01：V存儲器 00：其它
str_write(27) = &H84 '讀不同元件的代碼
str_write(28) = &H0
str_write(29) = &H0 '高位地址 地址轉換地16進制 （字節號*8+位號）\256
str_write(30) = &H0 '低位地址 地址轉換地16進制 （字節號*8+位號）Mod 256
str_write(31) = SumChk(str_write)
str_write(32) = &H16
Case 3 '讀輸入
ReDim str_write(0 To 32) As Byte '重新定義數組
str_write(0) = &H68
str_write(1) = &H1B
str_write(2) = &H1B
str_write(3) = &H68
str_write(4) = &H2
str_write(5) = &H0
str_write(6) = &H6C
str_write(7) = &H32
str_write(8) = &H1
str_write(9) = &H0
str_write(10) = &H0
str_write(11) = &H0
str_write(12) = &H0
str_write(13) = &H0
str_write(14) = &HE
str_write(15) = &H0
str_write(16) = &H0
str_write(17) = &H4 '讀
str_write(18) = &H1
str_write(19) = &H12
str_write(20) = &HA
str_write(21) = &H10
str_write(22) = &H2 '讀取位，字節，字，雙字（1，2，4，8）
str_write(23) = &H0
str_write(24) = &H2 '讀取數據個數
str_write(25) = &H0
str_write(26) = &H0 '存儲器類型，01：V存儲器 00：其它
str_write(27) = &H81 '讀不同元件的代碼
str_write(28) = &H0
str_write(29) = &H0 '高位地址 地址轉換地16進制 （字節號*8+位號）\256
str_write(30) = &H0 '低位地址 地址轉換地16進制 （字節號*8+位號）Mod 256
str_write(31) = SumChk(str_write)
str_write(32) = &H16
Case 4 '讀VW0—VW15
ReDim str_write(0 To 32) As Byte '重新定義數組
str_write(0) = &H68
str_write(1) = &H1B
str_write(2) = &H1B
str_write(3) = &H68
str_write(4) = &H2
str_write(5) = &H0
str_write(6) = &H6C
str_write(7) = &H32
str_write(8) = &H1
str_write(9) = &H0
str_write(10) = &H0
str_write(11) = &H0
str_write(12) = &H0
str_write(13) = &H0
str_write(14) = &HE
str_write(15) = &H0
str_write(16) = &H0
str_write(17) = &H4 '讀
str_write(18) = &H1
str_write(19) = &H12
str_write(20) = &HA
str_write(21) = &H10
str_write(22) = &H2 '讀取位，字節，字，雙字（1，2，4，8）
str_write(23) = &H0
str_write(24) = &H20 '以字節爲單位，連續讀取的字節數
str_write(25) = &H0
str_write(26) = &H1 '存儲器類型，01：V存儲器 00：其它
str_write(27) = &H84 '讀不同元件的代碼
str_write(28) = &H0
str_write(29) = &H0 '高位地址 地址轉換地16進制 （字節號*8+位號）\256
str_write(30) = &H0 '低位地址 地址轉換地16進制 （字節號*8+位號）Mod 256
str_write(31) = SumChk(str_write)
str_write(32) = &H16
Case 5 '讀輸出
ReDim str_write(0 To 32) As Byte '重新定義數組
str_write(0) = &H68
str_write(1) = &H1B
str_write(2) = &H1B
str_write(3) = &H68
str_write(4) = &H2
str_write(5) = &H0
str_write(6) = &H6C
str_write(7) = &H32
str_write(8) = &H1
str_write(9) = &H0
str_write(10) = &H0
str_write(11) = &H0
str_write(12) = &H0
str_write(13) = &H0
str_write(14) = &HE
str_write(15) = &H0
str_write(16) = &H0
str_write(17) = &H4 '讀
str_write(18) = &H1
str_write(19) = &H12
str_write(20) = &HA
str_write(21) = &H10
str_write(22) = &H2 '讀取位，字節，字，雙字（1，2，4，8）
str_write(23) = &H0
str_write(24) = &H2 '讀取數據個數
str_write(25) = &H0
str_write(26) = &H0 '存儲器類型，01：V存儲器 00：其它
str_write(27) = &H82 '讀不同元件的代碼
str_write(28) = &H0
str_write(29) = &H0 '高位地址 地址轉換地16進制 （字節號*8+位號）\256
str_write(30) = &H0 '低位地址 地址轉換地16進制 （字節號*8+位號）Mod 256
str_write(31) = SumChk(str_write)
str_write(32) = &H16
Case 6 '讀S0.0—S0.7
ReDim str_write(0 To 32) As Byte '重新定義數組
str_write(0) = &H68
str_write(1) = &H1B
str_write(2) = &H1B
str_write(3) = &H68
str_write(4) = &H2
str_write(5) = &H0
str_write(6) = &H6C
str_write(7) = &H32
str_write(8) = &H1
str_write(9) = &H0
str_write(10) = &H0
str_write(11) = &H0
str_write(12) = &H0
str_write(13) = &H0
str_write(14) = &HE
str_write(15) = &H0
str_write(16) = &H0
str_write(17) = &H4 '讀
str_write(18) = &H1
str_write(19) = &H12
str_write(20) = &HA
str_write(21) = &H10
str_write(22) = &H2 '讀取位，字節，字，雙字（1，2，4，8）
str_write(23) = &H0
str_write(24) = &H1 '讀取數據個數
str_write(25) = &H0
str_write(26) = &H0 '存儲器類型，01：V存儲器 00：其它
str_write(27) = &H4 '讀不同元件的代碼
str_write(28) = &H0
str_write(29) = &H0 '高位地址 地址轉換地16進制 （字節號*8+位號）\256
str_write(30) = &H0 '低位地址 地址轉換地16進制 （字節號*8+位號）Mod 256
str_write(31) = SumChk(str_write)
str_write(32) = &H16
Case 7 '讀C0
ReDim str_write(0 To 32) As Byte '重新定義數組
str_write(0) = &H68
str_write(1) = &H1B
str_write(2) = &H1B
str_write(3) = &H68
str_write(4) = &H2
str_write(5) = &H0
str_write(6) = &H7C
str_write(7) = &H32
str_write(8) = &H1
str_write(9) = &H0
str_write(10) = &H0
str_write(11) = &H0
str_write(12) = &H12 '&H8
str_write(13) = &H0
str_write(14) = &HE
str_write(15) = &H0
str_write(16) = &H0
str_write(17) = &H4 '讀
str_write(18) = &H1
str_write(19) = &H12
str_write(20) = &HA
str_write(21) = &H10
str_write(22) = &H1E '讀取位，字節，字，雙字（1，2，4，8）
str_write(23) = &H0
str_write(24) = &H1 '讀取數據個數
str_write(25) = &H0
str_write(26) = &H0 '存儲器類型，01：V存儲器 00：其它
str_write(27) = &H1E '讀不同元件的代碼
str_write(28) = &H0
str_write(29) = &H0 '高位地址 地址轉換地16進制 （字節號*8+位號）\256
str_write(30) = &H0 '低位地址 地址轉換地16進制 （字節號*8+位號）Mod 256
str_write(31) = SumChk(str_write)
str_write(32) = &H16
End Select
End If
MSComm1.InBufferCount = 0
MSComm1.OutBufferCount = 0
MSComm1.Output = str_write '發送命令
ik = 0
Timer1.Enabled = False '等待接收處理結束後再進行下一次的命令發送
Timer2.Enabled = True
Text5 = "0"
Shape6.BackColor = &HE0E0E0
End Sub
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Private Sub Timer2_Timer()
ik = ik + 1
If ik > 3 And Timer1.Enabled = False Then
Timer1.Enabled = True
End If
End Sub
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------