Overview
The SIMATIC TP 177A is a 6-inch mono/stereo touch panel that operates as a transfer-restricted slave on the MPI/PROFIBUS DP bus and as a PPI master/slave on the S7-200 PPI network. Because the panel was originally developed as the successor to the TD 200 text display, its download behavior differs from later Comfort/Universal panels: the first project load is forced over MPI or PPI, and only after a PROFIBUS-enabled project has been compiled into the panel does DP transfer become available. Selecting a single cable that handles all three load cases (commissioning, runtime download, and online diagnostics) is therefore a question of port count, driver stack support in WinCC flexible SP2 (32-bit), and the physical interface exposed by the PC (USB or RS-232).
This guide consolidates the technical constraints of the TP 177A against the S7-200 PPI/USS/Freeport bus and the WinCC flexible SP2 transfer channel, then ranks the three commercial candidates that solve the "single-cable" requirement: USB/PPI multimaster cable (6ES7 901-3DB30-0XA0), USB/MPI adapter, and PC Adapter USB A2 (6GK1571-0BA00-0AA0).
TP 177A Interface Architecture and Transfer Modes
The TP 177A exposes a single sub-D 9-pin female RS-485 port on the rear (X2/IF 1B) that is internally multiplexed between PPI, MPI, and PROFIBUS DP. The operating mode is selected by the configuration compiled into the panel with WinCC flexible, not by a hardware switch. The relevant entry is Project > Transfer > Transfer Mode inside WinCC flexible 2008 SP2.
| Mode | Baud Rate | Bus Profile | PC-Side Driver | Use Case |
|---|---|---|---|---|
| PPI | 9.6 / 19.2 / 187.5 kbit/s | S7-200 master/slave, multimaster token | S7-200 PPI/PC PPI cable | First load, S7-200 runtime |
| MPI | 187.5 kbit/s (default) up to 12 Mbit/s | S7-300/400, TP/OP, multimaster | PC Adapter USB A2, CP 5711 | First load, mixed fleet |
| PROFIBUS DP | 1.5 Mbit/s (default), up to 12 Mbit/s | DP master class 2 (PG) for transfer | PC Adapter USB A2, CP 5711, CP 5611 | Runtime reload after PROFIBUS project |
Cable Options Compared
Three cable families are compatible with the TP 177A rear port. Each is evaluated against the requirement to load a TP 177A project, connect to an S7-200 CPU 22x, and run online diagnostics on the same physical cable.
| Cable | MLFB / Order Number | PC-Side Interface | Panel/PLC Side | Bus Modes Supported | Notes |
|---|---|---|---|---|---|
| USB/PPI multimaster | 6ES7 901-3DB30-0XA0 | USB 1.1/2.0 | Sub-D 9-pin RS-485 to S7-200 Port 0/1 or TP 177A X2 | PPI only | Single-drop, panel acts as PPI master/slave. Cannot address MPI/DP nodes. |
| USB/MPI (USB-to-RS485) | Generic 6ES7 972-0CB20-0XA0 family (PC USB adapter, MPI only) | USB | Sub-D 9-pin | MPI only, not DP | Older USB/MPI variants may not support DP class-2 functions required for transfer. |
| PC Adapter USB A2 | 6GK1571-0BA00-0AA0 | USB 2.0 | Sub-D 9-pin RS-485 | PPI, MPI, PROFIBUS DP (up to 12 Mbit/s) | Single cable covers all three modes. Replaces legacy 6GK1571-1AA00. |
| CP 5711 | 6GK1571-1AA00-0AA0 (or -0AA0 regional) | USB 2.0 | Sub-D 9-pin | PPI, MPI, DP | PROFIBUS interface card emulator. Requires SIMATIC NET 12+ license; same multi-mode coverage as A2. |
The PC Adapter USB A2 (6GK1571-0BA00-0AA0) is the only single-cable solution that satisfies all three transfer modes without reconfiguration, which is why Siemens technical support entry 19109408 lists it as the preferred solution for the TP 177A. The official TP 177A technical data sheet, ID 21649471, also documents that configuration can be transferred via MPI/PROFIBUS DP or serial connection using a PC/PPI adapter cable.
S7-200 PPI Network Constraints
The S7-200 CPU 22x family communicates with the TP 177A on PPI by default. Two ports exist on most CPUs (Port 0 and Port 1); each can be assigned an independent PPI address. Standard commissioning practice is to keep Port 0 reserved for STEP 7-Micro/WIN and Port 1 for the panel link, although a multimaster PPI bus (TP 177A + PC/PPI) is supported when addresses are unique (range 1-31, address 0 reserved for master).
| Parameter | S7-200 CPU 22x Default | TP 177A Project Value |
|---|---|---|
| Baud rate | 9.6 kbit/s | 187.5 kbit/s (recommended) |
| Highest station address | 31 | 31 |
| Master/Slave mode | Slave (CPU) | Master (panel token holder) |
| Gap factors | Not applicable | Configure 1 if repeater-free |
For consistent behaviour with the TP 177A, raise the CPU Port 0 or Port 1 baud rate to 187.5 kbit/s using STEP 7-Micro/WIN > System Block > Communication Ports. Save to data block and reboot the CPU.
MPI / PROFIBUS DP Transfer Mode
When the TP 177A is part of a mixed S7-300/400 cabinet, the configuration link must be MPI or DP rather than PPI. In WinCC flexible SP2, open Project > Transfer > Transfer Mode and select the RS232/USB MPI/DP channel. The HMI connection in the connection editor must reference the MPI or PROFIBUS address of the PLC, not the PPI address.
The PC Adapter USB A2 is delivered with a DIP switch preset for PPI/MPI/DP auto-detect. The newer firmware (V2.0 and later) auto-bauds between 9.6 kbit/s and 12 Mbit/s, eliminating manual switch setting for the TP 177A.
Step-by-Step: Configuring Communication in WinCC Flexible SP2
- Open the project in WinCC flexible 2008 SP2 (32-bit). In Project > Transfer > Transfer Settings, set Mode to PPI for the initial load. Keep Search and Transfer enabled.
- Connect the USB/PPI multimaster cable (or PC Adapter USB A2) to the TP 177A X2 port and to a free USB port. Power the panel; wait for the loader screen to display "Connect to host...".
- In WinCC flexible, click Transfer > Transfer to Device. The transfer dialog should display the panel's PPI/MPI address (default 1) and the detected baud rate.
- For first-time load only, leave the project's HMI connection set to PPI with the S7-200 CPU address (default 2) and baud 187.5 kbit/s. Click Transfer.
- After the first load succeeds, return to the project, change the HMI connection to PROFIBUS DP (if desired) at the corresponding baud, recompile, and reload. From this point onward, DP transfer is selectable on the panel menu Main > Transfer > DP.
- To validate the cable, open Start > SIMATIC > ProSave, point it at the same interface, and click Device > Update. The TP 177A must reply with its firmware version (e.g.,
TP177A 6" mono V1.1.0).
PC Adapter USB A2 Detailed Specifications
| Parameter | Value |
|---|---|
| Order number (MLFB) | 6GK1571-0BA00-0AA0 |
| PC interface | USB 2.0 Type A, bus-powered |
| Bus interface | Sub-D 9-pin male, RS-485 isolated (1.5 kV) |
| Supported protocols | PPI, MPI, PROFIBUS DP-V0/V1/V2 master class 2 |
| Baud rate range | 9.6 kbit/s to 12 Mbit/s |
| Bus termination | Internal, switchable (terminating resistor 220 ohm + 390 ohm pull-up/pull-down) |
| Current consumption | Approx. 200 mA from USB |
| Driver stack | SIMATIC NET V12 SP1 or WinCC flexible SP2 integrated driver |
| Firmware updateable | Yes, via Set PG/PC Interface > PC Adapter USB A2 > Firmware Update |
| Status LEDs | PWR, USB, ACT, ERR |
For the TP 177A, the PC Adapter USB A2 is set in Set PG/PC Interface with the access point S7ONLINE (STEP7) > PC Adapter (USB). In WinCC flexible SP2, select Connection > RS232/USB PPI/MPI/DP Adapter. The adapter's integrated termination switch must be set to ON when the panel is at the bus end; otherwise leave it OFF and rely on the bus connector's built-in resistor.
USB/PPI Multimaster Cable (6ES7 901-3DB30-0XA0) Reference
The USB/PPI multimaster cable is the lowest-cost option and the recommended choice when the project is exclusively an S7-200 + TP 177A link. The cable contains an FTDI FT232BM-style USB-to-serial converter and a Siemens-proprietary ASIC that bridges the USB CDC serial stream to PPI multimaster. It supports only PPI bus profiles and cannot speak MPI or DP master class 2. It is therefore not suitable for engineering a mixed S7-300 cabinet.
| Parameter | Value |
|---|---|
| Order number | 6ES7 901-3DB30-0XA0 |
| PC interface | USB 1.1/2.0 Type A |
| PLC interface | Sub-D 9-pin male (RS-485, PPI multimaster) |
| Baud rate | 9.6 kbit/s and 187.5 kbit/s only |
| Isolation | None (functional ground only) |
| Supported by WinCC flexible SP2 | Yes, listed as PPI (USB) |
Pinout and Wiring Reference
The TP 177A, the S7-200 Port 0/1, and the PC Adapter USB A2 all use the Siemens standard PROFIBUS RS-485 pinout. Crossover is internal to the cable; do not use a null-modem adapter.
| Pin | Signal | Description |
|---|---|---|
| 1 | Shield | Functional ground, bonded to connector shell |
| 2 | M24 | 24 V ground reference (used only by older active PROFIBUS connectors) |
| 3 | RxD/TxD-P | Positive data line (B) |
| 4 | RTS | Request To Send, direction control |
| 5 | M5V | 5 V reference for bus termination |
| 6 | P5V | 5 V supply for bus termination |
| 7 | NC | Reserved |
| 8 | RxD/TxD-N | Negative data line (A) |
| 9 | NC | Reserved |
Transfer Mode Decision Matrix
| Project Composition | Required Cable(s) | Recommended Single Cable |
|---|---|---|
| TP 177A ↔ S7-200 CPU 22x only, PPI | USB/PPI multimaster or PC Adapter USB A2 | 6ES7 901-3DB30-0XA0 (lowest cost) |
| TP 177A ↔ S7-200, plus STEP 7-Micro/WIN online on the same CPU | PC Adapter USB A2 (multimaster PPI supported) | 6GK1571-0BA00-0AA0 |
| TP 177A ↔ S7-300/S7-400, MPI 187.5 kbit/s | PC Adapter USB A2, CP 5711, or CP 5611 A2 | 6GK1571-0BA00-0AA0 |
| TP 177A ↔ S7-300/S7-400, PROFIBUS DP 1.5 Mbit/s | PC Adapter USB A2, CP 5711, or CP 5611 A2 | 6GK1571-0BA00-0AA0 |
| Future re-targeting of the panel to a Comfort series or a TIA Portal project | PC Adapter USB A2 or CP 5711 | 6GK1571-0BA00-0AA0 |
Troubleshooting Common Faults
| Symptom | Likely Cause | Remediation |
|---|---|---|
| Transfer dialog reports "Device not found" | USB driver for PC Adapter not installed, or wrong COM port selected | Install SIMATIC NET or WinCC flexible SP2 driver; verify Set PG/PC Interface points to the correct USB instance |
| Transfer starts then aborts with "Timeout on TP 177A" | MPI/DP address collision or terminating resistor missing | Set unique MPI address on panel (1) and PLC (2); enable termination on the bus end connectors |
| USB/PPI cable works for STEP 7-Micro/WIN but WinCC flexible cannot transfer | WinCC flexible SP2 expects a different PPI access point | Change Set PG/PC Interface access point to S7ONLINE (PPI/USB) |
| Panel shows "Loader active" forever | Boot project is corrupt or version mismatch | Use ProSave to perform a manual firmware update, then transfer the WinCC flexible project again |
| DP transfer works only on second attempt | First-load restriction not yet satisfied | Perform initial load with PPI, then change HMI connection to DP and reload |
| CRC errors at 1.5 Mbit/s on long cable | Cable > 12 m, missing repeater, or missing termination | Use repeater (6GK1 500-0AA00), keep total bus length within PROFIBUS DP limits, verify termination at both ends only |
Field Commissioning Checklist
- Verify the panel firmware version against the WinCC flexible SP2 compatibility list (panel firmware < V2.0.0 supports WinCC flexible 2008; V2.0+ requires SP2 update 3 or later).
- Set the TP 177A's transfer mode in the project before download; the panel will not display the corresponding menu option if the compiled project does not include that mode.
- Match baud rate between S7-200 System Block, panel project, and cable's DIP switch (A2 auto-bauds, USB/PPI requires 187.5 kbit/s host setting).
- Save the project with Project > Compiler > Generate Sources when the target is being migrated to TIA Portal, to preserve tag references for
TP177A-V2-V3-V4device imports. - Document the cable MLFB in the cabinet drawing so a replacement is unambiguous; the PC Adapter USB A2 is field-proven and the only single-cable option spanning PPI, MPI, and DP.
Can a single cable handle TP 177A to S7-200 download and S7-300/400 diagnostics?
Yes. Use the PC Adapter USB A2 (6GK1571-0BA00-0AA0). It supports PPI 9.6/19.2/187.5 kbit/s, MPI 187.5 kbit/s to 12 Mbit/s, and PROFIBUS DP up to 12 Mbit/s, satisfying the TP 177A's first-load MPI/PPI rule and subsequent DP runtime transfers from a single piece of hardware.
Will the USB/PPI multimaster cable (6ES7 901-3DB30-0XA0) work for first-time panel loading?
Yes, but only on PPI. The cable supports 9.6 and 187.5 kbit/s PPI multimaster, which is sufficient for the TP 177A's mandated first load. It cannot speak MPI or PROFIBUS DP, so any future cabinet migration requires a different cable.
Why does WinCC flexible SP2 refuse a DP transfer on a brand-new TP 177A?
The TP 177A enforces a first-load rule: the initial project must be downloaded via PPI or MPI. After that first load, projects compiled with a PROFIBUS DP HMI connection can be reloaded over DP. The ProSave utility shows the same behavior on the device-update screen.
Is the CP 5711 a drop-in replacement for the PC Adapter USB A2?
Functionally, yes, for PPI/MPI/DP. The CP 5711 (6GK1571-1AA00) emulates a CP 5611 A2 over USB and needs SIMATIC NET V12 or later. For WinCC flexible SP2, the PC Adapter USB A2 is the simpler, fully integrated choice.
What baud rate should the S7-200 CPU use with the TP 177A?
Set the CPU Port 0 or Port 1 to 187.5 kbit/s in STEP 7-Micro/WIN System Block > Communication Ports. The TP 177A default project value is also 187.5 kbit/s, eliminating any baud-rate mismatch that would otherwise abort the first load.