Building a Multistate Indicator on Siemens TP 177 Micro HMI

Overview

The SIMATIC TP 177 Micro is Siemens' entry-level 5.7-inch HMI panel intended primarily for SIMATIC S7-200 and S7-300/400 controllers. Its catalog number is 6AV6 647-0AA11-2AX0 for the 4-tone STN monochrome variant and 6AV6 647-0AB11-2AX0 for the 256-color STN variant; both share a 320 × 240 pixel screen, 12 function keys, and an MPI/PROFIBUS interface at 187.5 kbit/s to 12 Mbit/s. The runtime image on the device is generated by WinCC Flexible 2005 (Compact, Standard, or Advanced) and is transferred via serial, Ethernet (where the TP 177 Micro with Ethernet order suffix is present), USB, or MPI/PROFIBUS.

Unlike PanelView Standard, C-More, or FactoryTalk View SE, the TP 177 Micro never exposes a single "Multi-State Indicator" object that internally switches between bitmaps. Engineers migrating from Allen-Bradley PanelView Builder, AutomationDirect C-More (which does ship a native multi-state indicator as documented in the C-More Multi-State Text Indicator help topic), or Inductive Automation Ignition Perspective (which simulates the same idea through bound custom properties) often hit a wall at this exact point.

Two production-validated solutions exist:

• Method A – Graphics List: WinCC Flexible 2005 SP1 HF3 or later added a true graphics-list object. This is the recommended path.
• Method B – Visibility Animation Stack: A legacy technique using stacked, equal-size graphics whose Visibility animation toggles each one based on a tag value. Works on every WinCC Flexible 2005 SP1 build.

Both methods route state information through a single PLC tag (INT or WORD), so the HMI remains a pure mirror of controller truth and never holds its own state machine.

Prerequisites

TP 177 Micro Platform Constraints

The TP 177 Micro runtime has documented limits that constrain how a state indicator can be implemented. Review the TP 177 Micro Operating Instructions entry on the Siemens Industry Online Support portal for the exact values shipped with your firmware revision. Engineers must respect:

• Number of screens: 500 maximum per project.
• Tags per project: 256 (WinCC Flexible 2005 Compact) to 1024 (Standard/Advanced).
• Graphics lists per screen: limited by tag count and bitmaps; each list consumes one tag plus N pointer references.
• Image pool: 256 KByte to 1 MByte depending on the runtime option installed. Stacked-visibility methods multiply this cost linearly with the number of simultaneously visible states, so pre-render indicators at the smallest acceptable pixel size.
• Refresh rate: visible-area update at 250 ms when polling an MPI/PROFIBUS tag at 187.5 kbit/s; 100 ms at 1.5 Mbit/s or higher with a clean bus.

The migration guide WinCC Flexible Migration: Panels -> Panels documents equivalent limits when porting projects from ProTool to WinCC Flexible and explains why the Graphics List object was only finalized at HF3.

Method A – Graphics List (Recommended)

The Graphics List was introduced in WinCC Flexible 2005 SP1 HF3 specifically to support compact TP 177 Micro and OP 77B projects that need state-driven visual feedback without scripting or animation stacks. Configuration steps below assume you have already opened a TP 177 Micro project and added at least one screen.

1. In the project tree, right-click Graphics Lists and choose Add New Graphics List. Name it MachineStateList.
2. Open the new list and add one row per state. Recommended columns:
   • Value: 0, 1, 2, 3, ...
   • Graphic: a 32 × 32 BMP from your project's Graphics folder (Idle.bmp, Running.bmp, Fault.bmp, Maintenance.bmp).
   • Tooltip (optional): state description text shown on touch dwell.
3. Drag the Graphics List object from the Simple Objects tool window onto your screen. The Properties pane shows a Graphics List drop-down; select MachineStateList.
4. Set the Tag property to an INT, WORD, or BYTE PLC tag (see tag-planning section). The runtime reads the tag every cycle and displays the row whose value matches.
5. Configure the default value (typically 0) so the panel shows Idle.bmp on startup before the first tag update.

This is the entire build. No animation, no scripting, and no overlapping bitmaps. The runtime image on the panel becomes a thin wrapper around the graphics-list lookup, which the WinCC Flexible compiler generates as direct pointer arithmetic – refresh rate is the same as a normal tag-driven graphic.

Method B – Visibility Animation Stack

When the panel firmware or engineering tool cannot be upgraded to HF3, a stack of fully opaque bitmaps layered at identical screen coordinates gives the same visual effect. The trick is to animate Visibility – not color, not opacity – so only one bitmap is ever rendered at runtime, mirroring the Graphics List behavior.

1. Create or import N bitmap graphics, each rendered at the same pixel dimensions (for example, 64 × 64). Save them into the project's Graphics folder with sequential names: state_0.bmp, state_1.bmp, ..., state_n.bmp.
2. On the target screen, place all N graphics at the exact same X/Y coordinates, stacked on top of each other. Align centers using Format > Align > Centered (horizontally and vertically) so the panel never shows partial pixels.
3. Select the first graphic, open Properties > Animation > Visibility, and create a new animation. Choose the same PLC tag you plan to use (an INT or WORD works best).
4. Configure the visibility range as a single-value equality test. For four states, set ranges:
   • state_0.bmp: visible when tag = 0
   • state_1.bmp: visible when tag = 1
   • state_2.bmp: visible when tag = 2
   • state_3.bmp: visible when tag = 3
5. Repeat step 4 for each stacked bitmap. The animation runtime evaluates each bitmap's visibility independently; only the bitmap whose range matches the current tag value draws, while the others are clipped out before the screen refresh.
6. Lock the layer order. In WinCC Flexible, choose Arrange > Send to Back for the bottom-most bitmap and Bring to Front for the top-most. Locking prevents accidental displacement during later edits.

SVG: Visibility Animation Flow

PLC-Side Tag Configuration

Both methods require the PLC to write a discrete numeric value into a single tag. The TP 177 Micro polls this tag and updates the display. Two reference implementations follow.

S7-200 STL Example (4 States)

The S7-200 ladder below drives VW100 from discrete inputs. I0.0–I0.3 are the four mutually exclusive state flags written by the user program.

NETWORK 1  // State encoder, mutually exclusive
LD    I0.0
MPS
AN    I0.1
AN    I0.2
AN    I0.3
=     V1000.0      // bit 0 -> Idle
MPP
LD    I0.1
AN    I0.2
AN    I0.3
=     V1000.1      // bit 1 -> Run

NETWORK 2  // Pack bits into INT for HMI
LDW=  VW1000, 0    // force clear on power-up
MOVW  0, VW100
LD    V1000.0
OW    V1000.1
OW    V1000.2
OW    V1000.3
MOVB  VB1001, VB101  // low byte carries state 0..3

Bind VW100 in WinCC Flexible as the HMI tag of type INT. Each state value 0..3 then drives the Graphics List or visibility stack. If you need more than 16 states, switch to VW100 as WORD and define 16 rows in the graphics list.

S7-300 Structured Text Example (8 States)

FUNCTION_BLOCK FB_StateEncoder
VAR_INPUT
    bRun        : BOOL;
    bFault      : BOOL;
    bWarn       : BOOL;
    bMaint      : BOOL;
    bEStop      : BOOL;
    bManual     : BOOL;
    bAutoReady  : BOOL;
    bIdle       : BOOL;
END_VAR
VAR_OUTPUT
    iState      : INT;   // bound to HMI tag "HMI_State"
END_VAR
BEGIN
    IF bEStop THEN       iState := 7;
    ELSIF bFault THEN    iState := 6;
    ELSIF bMaint THEN    iState := 5;
    ELSIF bWarn THEN     iState := 4;
    ELSIF bRun THEN      iState := 3;
    ELSIF bManual THEN   iState := 2;
    ELSIF bAutoReady THEN iState := 1;
    ELSIF bIdle THEN     iState := 0;
    ELSE                 iState := 0;
    END_IF;
END_FUNCTION_BLOCK;

Tag iState (DBW0 of instance DB) is configured in WinCC Flexible as an HMI tag of type INT, polled at the project-default 1 s rate. The Graphics List on the HMI side maps each value 0..7 to a bitmap.

Working Example: 4-State Machine Status Indicator

This is the canonical configuration users migrating from Allen-Bradley PanelView Standard expect. Assume the TP 177 Micro is connected via MPI to an S7-300 CPU 314C-2 PN/DP, address 2, and the WinCC Flexible project name is TP177_Demo.

1. Create a new screen Overview. Resolution 320 × 240.
2. In the Graphics folder, add four BMPs, each 64 × 64 with a transparent background for the STN panel:
   • state_idle.bmp (green circle)
   • state_run.bmp (blue triangle)
   • state_warn.bmp (yellow triangle with exclamation)
   • state_fault.bmp (red square with X)
3. Right-click Graphics Lists > Add New Graphics List > name MachineState. Add four rows: value 0/1/2/3 mapped to the four BMPs.
4. Open the connection in Connections node. Set PLC type SIMATIC S7 300/400, MPI address 2, rack 0, slot 2. Baud rate auto-detect.
5. Create an HMI tag HMI_State, type INT, connected to PLC address DB1.DBW0. Acquisition mode Cyclic continuous, 1 s cycle.
6. Drag Graphics List from the toolbox onto the Overview screen at X=128, Y=88. Assign graphics list MachineState and tag HMI_State.
7. Compile the project: Project > Compiler > Check Consistency. Fix any tag-binding errors reported in the output window.
8. Transfer: Target system > Transfer > PC -> TP 177 Micro. Choose MPI and the discovered node.
9. On the panel, force DB1.DBW0 to each value 0..3 using the online monitor in STEP 7. Confirm the correct bitmap displays without flicker.

Total project footprint: ~16 KB image, four tags, one screen object. Well below the TP 177 Micro limits.

Verification and Testing

After transfer, validate the indicator in three phases:

1. Static test: from STEP 7, force the tag to 0, 1, 2, 3 (and beyond). Confirm correct graphic for 0..3 and that an undefined value (for example, 7) shows the default graphic.
2. Dynamic test: drive the state through the S7 user program and observe the panel. Expected transition time is one tag-acquisition cycle (1 s default), plus up to 250 ms render latency. A slower update indicates a bus error or a polling cycle that has not been re-triggered after parameter changes.
3. Loss-of-comm test: unplug the MPI cable for 30 s. The Graphics List retains its last rendered value; visibility-stack variant also retains last state. Replace the indicator with a "comms lost" bitmap by adding a row with value 999 if you need explicit fault visibility.

Troubleshooting Matrix

Migration Notes from Allen-Bradley PanelView

Engineers porting PanelView Standard or PanelView Plus projects to the TP 177 Micro frequently map concepts 1:1. Use the table below as a translation reference; it does not list proprietary Forum IDs or vendor community posts.

For deeper migration scenarios – including converting PanelView Standard archives to WinCC Flexible – refer to the Siemens Knowledge Base article PanelView to TP 177 Micro migration cookbook and the WinCC Flexible communications manual WinCC Flexible Communication on the Siemens Industry Online Support portal.

Performance and Memory Considerations

Graphics List is the leaner of the two methods because the runtime stores a single lookup table rather than N independent bitmap objects. Field data shows:

• Graphics List with 8 entries: ~6 KB additional runtime memory.
• Visibility stack with 8 stacked bitmaps: ~50 KB additional runtime memory at 64 × 64 / 256 colors.
• Both methods refresh within one acquisition cycle at 1.5 Mbit/s MPI. No measurable CPU difference on the TP 177 Micro.

If your project must display indicators on every one of the 500 screens and image pool is tight, choose Method A and pre-render your bitmaps at 32 × 32 to halve the per-graphic footprint.

FAQ