Siemens HMI I/O Status Screen in TIA Portal: Wiring, SCATTER, Text Lists and a Live DI/DO View

• One screen and about twenty HMI tags cover 60 inputs and 20 outputs.
• Text lists carry the descriptions, so a rename never touches the PLC.
• NC contacts are shown as NC and turn the row red when they open.

I/O plan and hardware

The example is a sealed quench heat-treatment furnace. The I/O count is fixed at 60 digital inputs, 20 analog inputs, 20 digital outputs and 10 analog outputs, with the digital descriptions taken from the project text lists. Every card keeps spares for later changes.

Set the analog start addresses by hand (Device view → module → Properties → I/O addresses) to 100, 116 and 132 for the AI cards and 100, 108 and 116 for the AQ cards. Fixed addresses keep the tag list valid when a card is added later. The same approach is shown step by step in Siemens device configuration and tag creation.

Stage 1Terminal wiring drawings (EPLAN style)

Twelve drawing sheets in the layout an EPLAN P8 PLC overview uses: column grid, title block, terminal strip numbers, device tags and the PLC channel with its address. Use the selector to page through the rack, the four DI sheets, two DQ sheets, three AI sheets and two AQ sheets.

Stage 2PLC tags – copy and paste

144 tags: 8 DI byte tags and 4 DQ byte tags for SCATTER, then every bit and analog channel. The byte tags replace names such as Tag_1, which tell a maintenance engineer nothing.

1. Fast way: click Copy for TIA tag table, open the IO_List tag table, click the first empty Name cell and press Ctrl+V. Name, data type and address fill in.
2. With comments: click Copy for Excel import, paste into cell A1 of a sheet named PLC Tags, save as .xlsx, then in the tag table use Import. This version also brings the comments and HMI access flags.

DI_Byte_0	Byte	%IB0
DI_Byte_1	Byte	%IB1
DI_Byte_2	Byte	%IB2
DI_Byte_3	Byte	%IB3
DI_Byte_4	Byte	%IB4
DI_Byte_5	Byte	%IB5
DI_Byte_6	Byte	%IB6
DI_Byte_7	Byte	%IB7
DQ_Byte_0	Byte	%QB0
DQ_Byte_1	Byte	%QB1
DQ_Byte_2	Byte	%QB2
DQ_Byte_3	Byte	%QB3
DI_0_0_Charge_Fork_Backward	Bool	%I0.0
DI_0_1_Discharge_Fork_Backward	Bool	%I0.1
…  (144 rows in total – use the copy button)

Stage 3The HMI_Status DB – copy and paste

The DB matches the addresses in the ladder: Card_No at DBB0 and DI.Inp at DBX2.0. It is a standard (not optimized) DB so those absolute addresses stay fixed. DI_NC_Mask holds one bit per NC contact, already filled from the text list Input Add C.

1. Copy the source, save it as HMI_Status.db.
2. Project tree → External source files → Add new external file → pick the file.
3. Right-click it → Generate blocks from source. Set the DB number to 1 in its properties if TIA chose another.

DATA_BLOCK "HMI_Status"
{ S7_Optimized_Access := 'FALSE' }
VERSION : 0.1
   STRUCT
      Card_No : Byte;          // DI byte shown on HMI (0..7)   -> %DB1.DBB0
      Card_No_DQ : Byte;       // DQ byte shown on HMI (0..2)   -> %DB1.DBB1
      DI : Struct              // -> %DB1.DBX2.0
         Inp : Array[0..7] of Bool;   // SCATTER of selected %IB
      END_STRUCT;
      DQ : Struct              // -> %DB1.DBX4.0
         Out : Array[0..7] of Bool;   // SCATTER of selected %QB
      END_STRUCT;
      Filter_DI : Byte;        // 0 All, 1 ON, 2 OFF, 3 NC only, 4 Faults
      Filter_DQ : Byte;        // 0 All, 1 ON, 2 OFF
      Show_DI : Array[0..7] of Bool;      // row visibility on HMI
      Show_DQ : Array[0..7] of Bool;
      DI_Fault : Array[0..7] of Bool;     // NC contact open
      DI_Changed : Array[0..7] of Bool;   // flashes until Clear
      DQ_Changed : Array[0..7] of Bool;
      DI_Prev : Array[0..7] of Bool;
      DQ_Prev : Array[0..7] of Bool;
      Prev_Card : Byte;
      Prev_Card_DQ : Byte;
      Clear_Changed : Bool;    // HMI button, PLC resets it
      DI_On_Count : USInt;
      DI_Fault_Count : USInt;
      DQ_On_Count : USInt;
      DI_NC_Mask : Array[0..7] of Byte := [16#27, 16#07, 16#07, 16#03, 16#03, 16#03, 16#03, 16#03];  // 1 = NC contact
   END_STRUCT;
BEGIN
END_DATA_BLOCK

Stage 4SCATTER ladder for every byte

One network for inputs and one for outputs. Each branch compares Card_No with a constant and, only on its own byte, runs SCATTER from the byte tag into the DB array. Only one branch is true at a time, so the array always holds the byte the operator picked.

Shorter alternative in SCL

The eight branches can be replaced by PEEK, which reads the input byte whose number is in Card_No. Use it when you are comfortable with indirect addressing; the ladder version is easier for maintenance staff to follow online.

// One-line alternative to the 8 branches of Network 1 (SCL network or FC)
// #b : Byte (Temp)
#b := PEEK(area := 16#81,              // 16#81 = process image inputs
           dbNumber := 0,
           byteOffset := "HMI_Status".Card_No);
SCATTER(IN := #b, OUT => "HMI_Status".DI.Inp);

Stage 5Filter, NC fault and change logic

The HMI only shows bits; this FC decides which rows are visible, which NC contacts are open, and which bits changed since the byte was opened. Generate it from source like the DB and call it in OB1 directly after Networks 1 and 2.

FUNCTION "FC_HMI_IO_Status" : Void
{ S7_Optimized_Access := 'TRUE' }
VERSION : 0.1
   VAR_TEMP
      i : Int;
      card : Int;
      on : Bool;
      ncBits : Array[0..7] of Bool;
   END_VAR

BEGIN
	// Call in OB1 AFTER the two SCATTER networks.
	// 1. Keep the HMI byte numbers inside the real hardware
	IF "HMI_Status".Card_No > 7 THEN
	    "HMI_Status".Card_No := 7;
	END_IF;
	IF "HMI_Status".Card_No_DQ > 2 THEN
	    "HMI_Status".Card_No_DQ := 2;
	END_IF;
	#card := BYTE_TO_INT("HMI_Status".Card_No);
	
	// 2. NO/NC pattern of the selected DI byte, one Bool per bit
	SCATTER(IN := "HMI_Status".DI_NC_Mask[#card],
	        OUT => #ncBits);
	
	// 3. New byte selected or Clear pressed: forget old changes
	IF ("HMI_Status".Card_No <> "HMI_Status".Prev_Card) OR "HMI_Status".Clear_Changed THEN
	    FOR #i := 0 TO 7 DO
	        "HMI_Status".DI_Changed[#i] := FALSE;
	        "HMI_Status".DI_Prev[#i] := "HMI_Status".DI.Inp[#i];
	    END_FOR;
	END_IF;
	IF ("HMI_Status".Card_No_DQ <> "HMI_Status".Prev_Card_DQ) OR "HMI_Status".Clear_Changed THEN
	    FOR #i := 0 TO 7 DO
	        "HMI_Status".DQ_Changed[#i] := FALSE;
	        "HMI_Status".DQ_Prev[#i] := "HMI_Status".DQ.Out[#i];
	    END_FOR;
	END_IF;
	"HMI_Status".Prev_Card := "HMI_Status".Card_No;
	"HMI_Status".Prev_Card_DQ := "HMI_Status".Card_No_DQ;
	"HMI_Status".Clear_Changed := FALSE;
	
	// 4. Digital inputs: fault, change, filter, counters
	"HMI_Status".DI_On_Count := 0;
	"HMI_Status".DI_Fault_Count := 0;
	FOR #i := 0 TO 7 DO
	    #on := "HMI_Status".DI.Inp[#i];
	    "HMI_Status".DI_Fault[#i] := #ncBits[#i] AND NOT #on;
	    IF #on <> "HMI_Status".DI_Prev[#i] THEN
	        "HMI_Status".DI_Changed[#i] := TRUE;
	    END_IF;
	    "HMI_Status".DI_Prev[#i] := #on;
	    CASE BYTE_TO_INT("HMI_Status".Filter_DI) OF
	        1: "HMI_Status".Show_DI[#i] := #on;
	        2: "HMI_Status".Show_DI[#i] := NOT #on;
	        3: "HMI_Status".Show_DI[#i] := #ncBits[#i];
	        4: "HMI_Status".Show_DI[#i] := "HMI_Status".DI_Fault[#i];
	        ELSE "HMI_Status".Show_DI[#i] := TRUE;
	    END_CASE;
	    IF #on THEN
	        "HMI_Status".DI_On_Count := "HMI_Status".DI_On_Count + 1;
	    END_IF;
	    IF "HMI_Status".DI_Fault[#i] THEN
	        "HMI_Status".DI_Fault_Count := "HMI_Status".DI_Fault_Count + 1;
	    END_IF;
	END_FOR;
	
	// 5. Digital outputs: change, filter, counter
	"HMI_Status".DQ_On_Count := 0;
	FOR #i := 0 TO 7 DO
	    #on := "HMI_Status".DQ.Out[#i];
	    IF #on <> "HMI_Status".DQ_Prev[#i] THEN
	        "HMI_Status".DQ_Changed[#i] := TRUE;
	    END_IF;
	    "HMI_Status".DQ_Prev[#i] := #on;
	    CASE BYTE_TO_INT("HMI_Status".Filter_DQ) OF
	        1: "HMI_Status".Show_DQ[#i] := #on;
	        2: "HMI_Status".Show_DQ[#i] := NOT #on;
	        ELSE "HMI_Status".Show_DQ[#i] := TRUE;
	    END_CASE;
	    IF #on THEN
	        "HMI_Status".DQ_On_Count := "HMI_Status".DQ_On_Count + 1;
	    END_IF;
	END_FOR;
END_FUNCTION

Stage 6Text and graphics lists (same format as g.xlsx)

The text lists follow the naming of the project export: Input Add b holds the description of bit b for every byte, Input Add C b holds NO or NC, and the value of each entry is the byte number. One new set, Input Address b, shows the address as text so column 1 is a single clean field.

Copy both sheets, paste each into its own sheet of one Excel file with the names TextList and TextListEntry, save, then import in the Text and graphic lists editor of the HMI device.

Name	ListRange	Comment [en-US]
Input Status	Decimal	<No value>
Output Status	Decimal	<No value>
IO Filter	Decimal	<No value>
Input Address 0	Decimal	<No value>
Input Add 0	Decimal	<No value>
Input Add C 0	Decimal	<No value>
Input Address 1	Decimal	<No value>
…  (51 text lists)

Name	Parent	DefaultEntry	Value	Text [en-US]	FieldInfos
Text_list_entry_1	Input Address 0		0	%I0.0	
Text_list_entry_2	Input Address 0		1	%I1.0	
Text_list_entry_3	Input Address 0		2	%I2.0	
Text_list_entry_4	Input Address 0		3	%I3.0	
Text_list_entry_1	Input Add 0		0	CHARGE FORK BACKWARD	
Text_list_entry_2	Input Add 0		1	DISCHARGE FORK BACKWARD	
Text_list_entry_3	Input Add 0		2	REAR DOOR OPEN LIMIT SWITCH	
Text_list_entry_4	Input Add 0		3	FRESH CHARGE ENTRY SAFE CP(1)	
Text_list_entry_1	Input Add C 0		0	NC	
Text_list_entry_2	Input Add C 0		1	NC	
Text_list_entry_3	Input Add C 0		2	NC	
Text_list_entry_4	Input Add C 0		3	NC	
…

Graphics lists

Take a grey lamp, a green lamp and a red warning symbol from the WinCC graphics collection (or import your own PNGs) and use them in a Graphic I/O field, mode Output, next to the status text.

Problems found in the supplied text lists

These were corrected in the copy-paste data above. Fix them in the project as well so the export and the drawing agree.

Stage 7HMI screen and animations

Build one row, test it, then copy it seven times and change only the row number b in the text list names and tag indexes. The table lists every object of row b.

For outputs, copy the screen and swap Card_No → Card_No_DQ, DI.Inp → DQ.Out and Input → Output in the text list names. Drop the NC filter and the fault animation. Layout rules for fonts and colours are in HMI screen design best practices, and I/O field details in HMI I/O fields and setpoint entry.

Stage 8Live simulator – perform and test

This works like the finished panel. Change the byte, click a status lamp to simulate the field, try every filter, and type an address such as I2.3 to jump straight to it. The dark line under the table shows what the PLC is doing at that moment.

Test checklist

• Card_No 0 … 7 changes all eight descriptions and addresses together.
• Forcing or bridging an input turns its lamp green and the row flashes yellow until Clear.
• Opening an NC contact turns the row red and raises the fault counter.
• Typing 9 in the byte field is refused by the tag limits; the FC also clamps it to 7.
• Each filter shows only matching rows; All brings every row back.

More animations worth adding

• Analog status page. Same byte idea for channels: Card_No picks an AI card, rows show tag, scaled value, a bar graph and the raw value. Raw 32767 on a 4–20 mA channel means wire break, so colour that row red. Scaling is covered in PLC analog input scaling.
• Byte overview strip. Eight small boxes, one per byte, each showing its ON count and turning red when DI_Fault_Count for that byte is above zero. Touching a box sets Card_No.
• Last change time. Store RD_SYS_T in an array when a bit changes and show it in a fifth column; it helps prove intermittent limit switches.
• Force indication. Show a yellow banner when the CPU has forced I/O, read from the diagnostic buffer, so nobody leaves forces behind after testing.
• Access level. Let operators view only; give the Clear button and forcing tools to the maintenance user group as in HMI user administration.

Practice notes

Troubleshooting

For hardware faults behind a bad signal, see Siemens PLC diagnostics and troubleshooting.