SINUMERIK 810M GA3 / 820 GA3: Resolving PCP/PCA File Transfer Failures via V24 Interface

The SINUMERIK 810M GA3 and 820 GA3 are member of the early-1990s Siemens CNC platform (Software Version 3) that retain an integrated SIMATIC S5 PLC for spindle, axis, and auxiliary-function handling. Field engineers servicing these controls still rely on the V24 (RS-232C) interface and the legacy STEP 5 / SINCOM toolset to load PCP (PLC program) and PCA (PLC alarm text) files. A common service call: the upload PC reports the file as sent, the control briefly flashes PCP on the screen, the prompt disappears, and no file lands in user memory. The same symptom occurs for PCA. This reference documents the root cause, the required pre-conditions, and the verified recovery sequence originally captured in the GA3 installation guide and refined through field experience.

1. Problem Description

During a V24 file transfer the host (PC running SINCOM/STEP 5) successfully sends a .PCP (PLC program binary) and a .PCA (PLC alarm text) file. The 810/820 screen momentarily shows PCP for approximately one to two seconds and then the prompt reverts to the previous state with no confirmation. Subsequent directory inspection shows the file is not resident in user memory. Re-attempts at higher and lower baud rates, and even using a known-good donor .S5D file from a sister machine, yield the same outcome.

The issue is reproducible across multiple 810 GA3 units of the same software revision when the procedure is started directly in Initial Clear Mode without first loading the machine data files that prime the PLC memory area. The behaviour is by design: the control's Initial Clear state withholds permission to write to the PLC program and alarm-text partitions until the matching machine data files are present.

2. Root Cause Analysis

The SINUMERIK 810/820 GA3 separates the CNC and PLC user memories. The PLC side is loaded with three independent object classes:

• TEA1 – NC setting/machine data (loaded as .TEA or .TEA1).
• TEA2 – PLC machine data, including the interface and PLC-specific setting data (loaded as .TEA2).
• PCP – the executable PLC program (ladder, statement list, or function block compiled in STEP 5 to a .PCP binary).
• PCA – the user-defined PLC alarm text file (paired with PCP, must be loaded after the program).

After a power-on, the control runs in the so-called Initial Clear Mode until the user explicitly leaves it. In this mode the PLC section is empty and is treated as unformatted. The control will accept TEA1, TEA2, and any NC data, but blocks the PCP and PCA writes because the PLC user-memory area has not yet been formatted. A common field misstep is to send the PCP/PCA pair first; the receiver acknowledges the file header and then discards the payload because the destination partition is not yet declared writable. The result is the brief PCP on-screen flash and silent return to the previous prompt.

Until the TEA2 has been read in and the user memory plus the alarm-text memory have been formatted, the PCA file transfer is locked. This is the behaviour described in the SINUMERIK 810 GA3 / 820 GA3 Installation Guide and is not a fault; it is a load-order guard.

3. Required Files and Their Function

The PCA file is intrinsically tied to the PCP file – alarm text references defined symbolic constants. Loading a PCA from a different PCP base is the leading cause of alarm-text upload flash-and-fail behaviour.

4. V24 Interface Configuration – Setting Data 5010 to 5016

The 810/820 GA3 exposes the COM1 parameters through Setting Data (SD) words 5010 through 5016. The values must be written before any file is transferred, and they must agree with the host (PC) terminal settings. The following configuration is the field-proven baseline for 9600 baud, 8 data bits, no parity, XON/XOFF handshake:

SD 5011 and SD 5013 share the same bit layout:

• Bits 0–3 (lower nibble) – baud rate code:
  0 = 50, 1 = 110, 2 = 134.5, 3 = 150, 4 = 300, 5 = 600, 6 = 1200, 7 = 2400, 8 = 4800, 9 = 9600.
• Bits 4–7 (upper nibble) – handshake / line discipline: C = software (XON/XOFF) with no echo.

SD 5016 selects the on-the-wire protocol. 0x28 (binary 0010 1000) is the SINUMERIK file-transfer protocol used by SINCOM; other values route the port to the DNC channel or to ASCII transparent mode and will not accept the binary PCP/PCA headers.

If the host runs SINCOM in binary mode, the PC side must be configured for 9600 / 8 / N / 1 with XON/XOFF, and the cable must be a Siemens V24 cable (full handshake, not a 3-wire null modem). The wiring of pins 4/5 (RTS/CTS) and 6/20 (DSR/DTR) is required for hardware handshaking variants; the recommended 0xC7 setting above uses software handshaking on pins 2/3 only and works with the standard 3-wire plus-chassis cable that Siemens shipped with the 810/820 series.

5. Step-by-Step Recovery Procedure

The procedure below is the verified recovery sequence. It assumes the V24 cable is connected, the PC is running SINCOM or an equivalent STEP 5 transfer utility, and the control is in a serviceable state.

1. Enter Initial Clear Mode. Power the control on. From the setup screen, navigate to Initial Clear and confirm. The control announces INITIAL CLEAR on the status line. All NC and PLC user memory is treated as unformatted at this point.
2. Read in TEA1 (NC parameters). From the host, transmit the .TEA1 file in binary protocol at 9600 baud. Wait for the control to display a positive acknowledgement (e.g., TEA1 OK or a green status indicator). The file becomes resident but the PLC area is still empty.
3. Read in TEA2 (PLC parameters). Transmit the .TEA2 file. This is the PLC machine-data file and is what defines the SD 5010–5016 values that gate the V24 port. If TEA2 was not previously loaded and saved, the SD values revert to defaults that may not match the host.
4. Verify SD 5010–5016. On the control, navigate to Setup > Setting Data and confirm:

   SD 5010 = 0
   SD 5011 = 1100 0111 (199 dec / 0xC7 hex)
   SD 5012 = 0
   SD 5013 = 1100 0111 (199 dec / 0xC7 hex)
   SD 5014 = 0
   SD 5015 = 0
   SD 5016 = 0010 1000 (40 dec / 0x28 hex)

   If any value is different (especially SD 5016), correct it and re-save before continuing.
5. Exit Initial Clear Mode to normal operating mode. Navigate to Setup, enter the password, and select END PW to terminate the password-protected initial-clear session. The control exits initial clear but does not yet power-cycle.
6. Power off, then power on, and re-enter Initial Clear Mode. The cold restart is mandatory. The PLC memory is re-initialised with the TEA2 settings applied. The control is again in Initial Clear Mode.
7. Format user memory and alarm-text memory. From the Initial Clear menu, execute Format User Memory (or Format PLC Memory depending on the HMI language revision) followed by Format Alarm Text Memory. Each format operation takes 5–15 seconds; wait for the success acknowledgement. The PLC user-memory partition is now declared writable.
8. Re-apply the V24 settings. Step 4 must be repeated because the format operation in step 7 may have reset the SD values to defaults. Confirm SD 5010–5016 once more and re-save.
9. Read in the PCA file (alarm text). With Initial Clear Mode still active and memory formatted, transmit the .PCA file. The control will accept it and the alarm-text partition becomes populated.
10. Read in the PCP file (PLC program). Transmit the .PCP file. The control will display PCP on the status line, hold the prompt for the duration of the transfer, and acknowledge with the success message.
11. Exit Initial Clear Mode and cold-restart. Leave Initial Clear Mode and perform a final NCK reset. The PLC starts executing the new program; alarm text is now active.
12. Verify the load. See Section 7.

6. Baud Rate and Protocol Reference

For 810/820 GA3 controls, the following baud rate codes apply to SD 5011 and SD 5013. Engineers servicing a fleet should standardize on 9600 baud (0xC7) to keep spares and PC scripts simple.

The SD 5016 protocol selector must be left at 0x28 (SINUMERIK file transfer) for binary file loads. Switching to 0x21 or other transparent modes is appropriate for DNC streaming of part programs but is not usable for the binary PCP/PCA pair.

7. Verification Steps

After the load, perform the following to confirm the recovery is complete:

1. PLC stop/run check. On the HMI, navigate to Diagnostics > PLC > Status. The PLC should report RUN with no OB1 cycle-time error. A stalled STOP with OB not loaded indicates the PCP file did not land.
2. Alarm text spot-check. Force a known PLC alarm (e.g., trigger a guard-door-open signal in the test program). The HMI should display the user-defined message, not a generic 700000-class number-only fault. If the number displays without text, the PCA file is empty or its symbolic IDs are out of sync with the PCP.
3. Checksum / CRC of file in user memory. From the host, request a directory listing or read the user memory back and compare against the source .PCP / .PCA. Byte counts must match exactly.
4. NCK reset test. Perform an NCK reset and observe a clean cold restart. Any PLC-related alarm at this stage is a load-order regression and the sequence in Section 5 must be repeated.
5. Make a fresh in-control backup. Once the load is verified, perform a Setup > Data Save (or equivalent) to write the new state to the NV-RAM / battery-backed SRAM so the change survives a power cycle.

8. Preventive Measures

• Maintain a versioned machine data archive. Store TEA1, TEA2, PCP, and PCA together for every machine. A PCP/PCA pair that is not matched to the active TEA2 will fail the load on first try.
• Standardize the V24 cable. Use the original Siemens V24 cable (part family 6FC9 341-1...) or a documented equivalent. A 3-wire null-modem cable will load ASCII files (TEA1, part programs) but will fail binary transfers at higher throughput because hardware handshaking is not present.
• Document the SD baseline. Print and laminate a card with the SD 5010–5016 reference values from Section 4 and keep it at the control. Field engineers arriving cold can restore the port in under a minute.
• Test the load on a bench unit first. If the project is rebuilt in STEP 5 and recompiled to a new PCP, verify the new PCP/PCA pair on a known-good 810/820 GA3 bench before scheduling a production cutover.
• Replace the PLC battery proactively. Loss of battery-backed SRAM is the leading cause of an unprompted Initial Clear, which then triggers the failure path described in this article. Replace the lithium backup battery on the prescribed service interval.

9. Troubleshooting Matrix

10. Related Documents and References

The procedure above is grounded in the original Siemens installation and commissioning documentation for the SINUMERIK 810 GA3 / 820 GA3 platform. Always consult the manufacturer's documentation for the exact software-version behaviour of your control.

• SINUMERIK 810 GA3 / 820 GA3 Installation Guide, Software Version 3, 01.93 Edition – Siemens Support entry 21899526.
• Siemens Product Support entry for the SINUMERIK 810 GA3 / 820 GA3 documentation set – Siemens Industrial Automation Support.

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