Simatic PC Adapter USB 6ES7 972-0CB20-0XA0 S7 MPI Profibus Setup

David Krause12 min read
Industrial NetworkingSiemensTutorial / How-to
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1. Problem Overview: PCMCIA Visibility in Windows Virtual XP

Engineers running legacy automation software such as STEP 7 V5.4 / V5.5 on Windows 7 frequently rely on Windows Virtual PC (XP Mode) as a sandbox. The most common failure mode reported in this configuration is the missing recognition of a PCMCIA CP 5611 / CP 5511 / CP 5512 communications processor by the virtual guest. Windows Virtual XP does not pass through CardBus/PCMCIA slot hardware to the guest OS; the card is enumerated by the host but remains opaque to vpc.exe and the vmguest.sys driver layer.

The recommended workaround is to abandon the PCMCIA adapter inside the VM and use a USB-attached MPI/Profibus converter: the Simatic PC Adapter USB A2 (Siemens catalog number 6ES7 972-0CB20-0XA0). USB devices are forwarded by Virtual PC, VMware Workstation, and Hyper-V, allowing STEP 7 to see the adapter as if it were a local device.

Scope of this guide: Installing the PC Adapter USB driver, configuring the PG/PC interface in STEP 7 V5.5, attaching the adapter to a virtual machine, and verifying communication with S7-200 (PPI), S7-300/400 (MPI), Profibus-DP slaves, and SINUMERIK 802D/840D/840Di.

2. Adapter Identification

The 6ES7 972-0CB20-0XA0 is the A2 generation of the Simatic PC Adapter USB family. Distinguish it from earlier siblings because the firmware and supported baud rates differ:

Catalog Number Designation Generation Firmware
6ES7 972-0CA20-0XA0 PC Adapter USB (original) A1 FW 1.x
6ES7 972-0CA33-0XA0 PC Adapter USB (TTY variant) A1 FW 1.x
6ES7 972-0CB20-0XA0 PC Adapter USB A2 A2 (current) FW 2.x
6ES7 972-0CB35-0XA0 PC Adapter USB A2 (TTY) A2 FW 2.x

The A2 model replaces the older 0CA20-0XA0 and is the only variant recommended for new installations with STEP 7 V5.5 SP2+ and TIA Portal V13+ on Windows 7 SP1 / Windows 10.

3. Hardware Specifications

Parameter Value
Siemens MLFB 6ES7 972-0CB20-0XA0
Host interface USB 1.1 Full-Speed (12 Mbps)
Bus interface RS-485 (MPI / PROFIBUS-DP), galvanically isolated
Baud rates MPI 19.2 / 187.5 kbps
Baud rates PROFIBUS 9.6 kbps to 12 Mbps
Max PROFIBUS segment length 1,200 m at 9.6 kbps / 100 m at 12 Mbps
Bus connector 9-pin D-sub female (PROFIBUS standard)
Termination External (use 6ES7 972-0BA30-0XA0 PROFIBUS connector with switchable termination)
Power USB bus-powered (no external PSU)
Current draw approx. 130 mA @ 5 V
Operating temp 0 °C to +60 °C
Driver package SIMATIC PC Adapter USB V2.0 (s7pcuaddp.inf / s7pusb2.sys)
Supported OS (native) Windows XP SP3 / 7 SP1 / Server 2008 R2 / 10
STEP 7 version V5.4 SP5 or higher (recommended V5.5 SP2+)

4. Compatibility Matrix

Target System Protocol Default Baud PC Adapter USB 0CB20 Notes
S7-200 (CPU 21x / 22x) PPI / MPI 9.6 / 19.2 kbps Supported Use PPI interface, set highest station address (HSA)
S7-200 Smart PPI / Modbus 187.5 kbps Partial Native driver incomplete; use S7-200 Smart Ethernet
S7-300 (CPU 31x / 31xT) MPI / PROFIBUS-DP 187.5 kbps Supported MPI is default
S7-400 (CPU 41x / 41xH) MPI / PROFIBUS-DP 187.5 kbps Supported MPI is default; PROFIBUS requires DP master role
S7-1200 PROFINET only 100 Mbps Not applicable Use Ethernet interface
S7-1500 PROFINET only 1 Gbps Not applicable Use Ethernet interface
SINUMERIK 802D / 802Dsl MPI (HMI Pro) 187.5 kbps Supported Configure PG/PC interface to MPI/PC Adapter
SINUMERIK 840D / 810D MPI / PROFIBUS 187.5 kbps / 1.5 Mbps Supported Use HMI Advanced or SinuCom NC
SINUMERIK 840Di PROFINET (native) 100 Mbps Not applicable Use NCU Ethernet port for commissioning
SINAMICS drives (CU310/CU320) PROFIBUS / PROFINET 1.5 Mbps / 100 Mbps Supported (DP only) STARTER / SCOUT via PROFIBUS DP
Third-party PROFIBUS slaves DP-V0/V1 up to 12 Mbps Supported as DP master PG/PC interface: PC Adapter (DP Master)

5. Prerequisites

  1. Hardware: PC with USB 1.1 / 2.0 / 3.x port, 6ES7 972-0CB20-0XA0, PROFIBUS cable (violet, 2-wire shielded), 9-pin D-sub with switchable termination if the device sits at a bus end.
  2. Host OS: Windows 7 SP1 (32-bit preferred for STEP 7 V5.5), Windows 10 21H2, or Windows 11 with driver compatibility mode.
  3. STEP 7 V5.5 SP2 (or later SP): Including the patch for Windows 7 / Server 2008 R2. Install the PC Adapter USB driver from the STEP 7 installation media (DVD) — SIMATIC PC Adapter USB V2.0 package.
  4. VMware Workstation 6.5 / 7.0 or later (if using VM). VMware 6 and 7 are known to work; version 15 / 16 / 17 with Windows 7 guest also work for users with newer toolchains.
  5. STEP 7 licence: Floating or local licence, plus a valid PG/PC interface assignment.
  6. Administrator rights on the host and guest.
Windows Virtual PC / XP Mode will NOT expose the CP 5611 PCMCIA card to the guest because the virtualisation layer does not emulate the PCMCIA controller. The 6ES7 972-0CB20-0XA0 USB adapter, however, is passed through because Windows Virtual PC supports USB device redirection. Switch to the USB adapter as the primary mitigation.

6. Installing the Simatic PC Adapter USB Driver

  1. Power on the host. Plug the 6ES7 972-0CB20-0XA0 into a USB port.
  2. Windows detects Simatic PC Adapter USB (A2). Cancel any automatic driver search.
  3. Open Device Manager, right-click the device → Update driver.
  4. Browse to C:\Program Files\Siemens\Automation\Simatic\S7PCT\Drivers\pcadapter_usb (default install path of STEP 7 V5.5). Select Have disk and point to pcadp_usb.inf.
  5. Confirm the driver installs as SIMATIC PC Adapter USB (A2). Status entry: Device working properly.
  6. Reboot if prompted.

7. Virtual Machine Configuration (VMware)

VMware Workstation 6 / 7 / 12+ exposes the 6ES7 972-0CB20-0XA0 to a Windows guest without third-party drivers. Configure as follows:

  1. Open the guest VM settings → USB Controller.
  2. Enable Show all USB input devices and USB compatibility 2.0 or 3.0.
  3. Plug the adapter into the host. Right-click the USB icon in the VM menu bar and choose Connect (Disconnect from Host).
  4. Inside the guest, repeat the driver installation step (Section 6) — the INF file is identical.
  5. Inside STEP 7 V5.5, the Set PG/PC Interface dialog will now list PC Adapter (MPI/DP) USB A2 and PC Adapter (PROFIBUS) USB A2.
Hyper-V: USB passthrough requires the host to run Windows Server with USB-server licences or Windows 10/11 Pro/Enterprise with Enhanced Session Mode. Performance is acceptable for MPI 187.5 kbps but may saturate at PROFIBUS 12 Mbps.

8. Physical Connection and Wiring

Pin (D-sub 9) Signal PROFIBUS wire color (violet cable)
3 RxD/TxD-P (B) Red
5 DGND (data ground) —
6 VP (+5 V bus termination) —
8 RxD/TxD-N (A) Green
  • Use only Siemens PROFIBUS cable 6XV1 830-0AH10 (violet, 22 AWG, characteristic impedance 150 Ω) for cable runs longer than 3 m.
  • Switch in the bus termination resistor at both physical bus ends only. The PC Adapter USB does NOT have internal termination — use a 6ES7 972-0BA30-0XA0 connector with switchable termination if the adapter is at the end of the segment.
  • Maintain shield bonding at every connector, earthed at one point only to avoid ground loops.

9. STEP 7 V5.5 PG/PC Interface Setup

  1. Open SIMATIC Manager → Options → Set PG/PC Interface….
  2. Under Interface Parameter Assignment Used, choose:
    • PC Adapter (MPI/DP) USB A2 — for MPI 187.5 kbps or PROFIBUS DP up to 1.5 Mbps.
    • PC Adapter (PROFIBUS) USB A2 — for PROFIBUS DP up to 12 Mbps (master class 1 / 2).
  3. Click Properties and set:
    • MPI: address = 0, transmission rate = 187.5 kbps, highest station = 31, timeout = 30 s.
    • DP Master: address = 0 (or 1 if a CPU also acts as DP master), profile = DP Master, transmission rate = Search (recommended) or fixed.
  4. Click Diagnostics to verify the adapter responds. The USB LED on the adapter should pulse green.
  5. Confirm the entry appears in Access Path of the Application as S7ONLINE → PC Adapter USB A2.

10. S7-200 PPI Communication

  1. Connect the PC Adapter USB to the S7-200 PPI port (Port 0 or Port 1 depending on CPU).
  2. In STEP 7 Micro/WIN V4.0 SP9, open Set PG/PC Interface.
  3. Select PC/PPI cable (PPI) — wait, PPI requires the PC/PPI cable (USB-PPI 6ES7 901-3DB30-0XA0). The PC Adapter USB does work with PPI via PC Adapter (MPI/DP) USB A2 as well, at 9.6 kbps and 19.2 kbps only.
  4. Set the PPI master address to 0 and the baud rate to match the CPU PPI setting (default 9.6 kbps on older CPU 21x).
  5. Click Communication → Search All Addresses. Verify the CPU appears at its configured PPI address.

11. S7-300 / S7-400 MPI Communication

  1. Wire the adapter to the S7-300 MPI port (X1 on CPU 31x) or S7-400 MPI port (X1 on CPU 41x).
  2. In SIMATIC Manager open the offline project (or create a new one with the correct CPU type).
  3. Select PLC → Accessible Nodes. The PG/PC interface scans the MPI bus for active stations.
  4. At 187.5 kbps with HSA 31, a CPU configured to address 2 (default) appears as Direct address 2 → S7-300 / S7-400.
  5. Double-click the entry to open the online view. Flash LED confirms addressing.
MPI 187.5 kbps is the only MPI baud rate reliably supported by the 6ES7 972-0CB20-0XA0. The original 0CA20-0XA0 supported 19.2 kbps only. Always verify firmware is FW 2.x before commissioning.

12. PROFIBUS DP Master Operation

  1. Open Set PG/PC Interface and select PC Adapter (PROFIBUS) USB A2.
  2. In Properties, switch the operating mode from DP Slave to DP Master. Set your master bus address (default 1).
  3. Set the transmission rate to Search for unknown bus speeds or fixed (commonly 1.5 Mbps or 12 Mbps).
  4. Open HW Config in STEP 7, insert the PC Station object, and load the configured DP master into the adapter.
  5. The PC Adapter USB now acts as a class-1 DP master and can search slaves via PLC → PROFIBUS → Diagnose Hardware.

13. SINUMERIK 802D / 840D / 840Di Connection

The PC Adapter USB connects to SINUMERIK HMI Pro / HMI Advanced for commissioning, NC program upload, and PLC debugging. Note that the 840Di is a PROFINET-only NCU; the USB adapter is not used for 840Di unless a separate PROFIBUS DP segment is present (e.g., I/O modules via DP/PN coupler).

  1. Wire the adapter to the SINUMERIK MPI port (X2 on CCU box / NCU box).
  2. On the HMI Pro system, open Commissioning → Communication Setup and assign PG/PC interface = PC Adapter (MPI/DP) USB A2.
  3. For 840D, the PLC portion (SINUMERIK PLC 840D sl) responds to MPI at 187.5 kbps and PROFIBUS DP up to 1.5 Mbps on the machine-side NCU port X101.
  4. For 802D, PPI/MPI mode is used; baud rate is fixed at 187.5 kbps in the standard configuration.
  5. Test with WinPCIN or SinuCom NC — if the tool sees the NCU at the configured MPI address, communication is live.

14. Performance vs PCMCIA and RS232-MPI

Adapter Bottleneck Effective Throughput (S7 upload) Hot-plug
CP 5611 (PCI, 6GK1161-1AA00) PCI bus 33 MHz Highest (1–12 Mbps PROFIBUS) No
CP 5511 / CP 5512 (PCMCIA) CardBus 32-bit Comparable to PCI No
PC Adapter USB A2 (0CB20) USB 1.1 FS 12 Mbps MPI 187.5 kbps, DP up to 1.5 Mbps comfortable / 12 Mbps achievable Yes
RS232-MPI (PC/PPI cable legacy) RS-232 38.4 kbps Lowest Yes

For STEP 7 V5.5 block upload/download, the PC Adapter USB A2 is more than sufficient — block transfer latency is governed by MPI 187.5 kbps, not USB. Engineers familiar with the PCI CP 5611 confirm the USB adapter is noticeably faster than the RS232-MPI cable and effectively equivalent to the PCMCIA CP 5512 for routine programming.

15. Troubleshooting Matrix

Symptom Likely Cause Corrective Action
Adapter not detected in Windows 7 Driver not installed, wrong INF Reinstall from STEP 7 DVD, force driver via Device Manager
Yellow exclamation in Device Manager, code 28 USB enumeration failure Try another port, replace USB cable, check WinUSB driver conflict
Adapter LED off USB power insufficient Use a powered hub or rear motherboard port
STEP 7 reports "Online: cannot establish connection" Wrong interface selected Open Set PG/PC Interface, pick PC Adapter (MPI/DP) USB A2
Search finds no nodes Wrong baud rate Set transmission rate to Search, verify HSA=31
Adapter visible, cannot go online to S7-200 PPI Wrong baud rate (19200 needed) Set baud rate to 19.2 kbps in PPI master config
Time-out after 30 s Bus termination missing or doubled Enable termination at end nodes only
SinuCom NC cannot reach 840D Wrong X-port on NCU Use X2 MPI on CCU, not X101 PROFIBUS
VMware guest does not see the adapter USB arbitration held by host VM → Removable Devices → Connect the adapter to the guest
Adapter disappears mid-session USB suspend / power saving Disable USB selective suspend in Power Options
Hyper-V Enhanced Session unable to attach USB not redirected Use RDP-style redirection; some adapters are blocked

16. Verification

  1. Open Set PG/PC Interface → Diagnostics. The readout shows Running on USB, the bus address, and the current baud rate.
  2. Run PLC → Accessible Nodes. At least one CPU should appear.
  3. Use PLC → Diagnostic → Hardware Diagnostic. CPU status reads OK, no diagnostic buffer entries related to communication.
  4. Upload a known block (e.g., OB1) and compare to the offline version — checksum mismatch would indicate corrupted transfer.
  5. Disconnect and reconnect the USB cable; STEP 7 should re-establish the link within 5 s.
  6. Reboot the host with the adapter plugged in. Windows should enumerate it within 30 s without user interaction.
Field tip: When supporting a fleet of S7-200/300/400 controllers on a USB-only programming laptop, carry one 6ES7 972-0CB20-0XA0, one 6GK1 571-1AA00 (CP 5711 USB / PROFIBUS) as a backup, and a 6ES7 972-0BA30-0XA0 termination connector. The combination covers every MPI/DP speed from 19.2 kbps to 12 Mbps.

Does the Simatic PC Adapter USB (6ES7 972-0CB20-0XA0) work with the SINUMERIK 840D?

Yes, the PC Adapter USB A2 communicates with the SINUMERIK 840D MPI port (X2 on CCU) at 187.5 kbps, and with the 840D PLC PROFIBUS DP port (X101) at 1.5 Mbps using HMI Advanced or SinuCom NC. The 840Di variant of the NCU is PROFINET-only and does not use the USB adapter unless an external PROFIBUS segment with a DP/PN coupler is installed.

Can Windows Virtual PC (XP Mode) forward the CP 5611 PCMCIA card to the guest?

No. Windows Virtual PC does not emulate the PCMCIA controller, so a CP 5611 / CP 5511 / CP 5512 installed in the host CardBus slot is not visible inside the guest. The recommended mitigation is to use the 6ES7 972-0CB20-0XA0 USB adapter, which is supported by Windows Virtual PC USB redirection.

Is the PC Adapter USB A2 faster than the legacy RS232-MPI cable?

Yes. The USB adapter supports PROFIBUS DP up to 12 Mbps and MPI at 187.5 kbps, while the legacy RS232-MPI cable is limited to 38.4 kbps. For STEP 7 V5.5 block transfers the USB adapter is several times faster and is effectively equivalent to the PCMCIA CP 5512 for daily programming.

What driver version is required on Windows 7 SP1?

Install STEP 7 V5.5 SP2 or later, which includes the SIMATIC PC Adapter USB V2.0 driver package (pcadp_usb.inf / s7pusb2.sys). Earlier STEP 7 V5.4 SP3 / SP4 versions work but require the driver to be loaded manually from the DVD.

Which VMware version is recommended for running STEP 7 V5.5 with the USB adapter?

VMware Workstation 6.5 or 7.0 with a Windows XP / Windows 7 32-bit guest is the most widely validated combination. VMware Workstation 15 / 16 / 17 with a Windows 10 32-bit guest also works, provided the USB controller compatibility is set to 2.0 or 3.0 and the device is manually connected to the guest from the VM menu.

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David KrauseIndustrial Controls Specialist – Siemens Platforms

Industrial controls specialist focused on Siemens SIMATIC S7 platform, from the S7-300/400 series through the latest S7-1200/1500 controllers. Expert in TIA Portal configuration and WinCC SCADA integration.

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