Resolving S7-1200 FW 4.2 HSC STOP Fault on TIA V13 Projects

When a S7-1200 CPU originally configured for firmware V4.0 in TIA Portal V13 is replaced with a V4.2 module, the controller can transition to STOP on the first power-cycle after download. The diagnostic buffer points to a High Speed Counter (HSC) object referenced by a HW_ID value (typically 257 for HSC 1, 261 for HSC 2 on the 1214C). Disabling the HSC clears the fault, but that defeats the purpose of the counter. The proper fix is to align the engineering project with the V4.2 firmware using a TIA Portal release that supports it.

Affected Hardware and Order Numbers

The fault was reproduced on the following configuration:

The CPU functional state (FS) was FS 05. The HSC channels involved were HSC 1 and HSC 2, both standard S7-1200 onboard high-speed counters. Per the official Siemens firmware release notice (entry ID 109741461), V4.2 is declared replacement-compatible with V4.0 and V4.1, but only when the project is built with an engineering system that knows about V4.2 — which TIA Portal V13 SP1 does not.

Diagnostic Buffer Event Sequence

The diagnostic buffer of the V4.2 CPU showed a consistent pattern after power-off / power-on:

1. Event 1 — Power-on (cold restart) of a configured HSC module.
2. Configuration validation step rejects the HSC object because the internal slot/HW-ID mapping of the V4.0 project does not match the V4.2 firmware's HSC descriptor table.
3. Diagnostic event Object under HW_ID 257 / HSC is raised; the OB priority is escalated to a startup error and the CPU enters STOP.

The relevant HW_ID values on the S7-1200 CPU 1214C are assigned by the TIA Portal hardware editor. Typical default IDs for onboard resources on this CPU are:

Root Cause

Two separate but interacting conditions cause the fault:

1. Firmware version mismatch. The TIA V13 project stores the firmware version of every device as a hard parameter. When the project is downloaded to a CPU whose actual firmware is greater than the configured version, TIA warns about a downgrade/inconsistency. The default behavior of the V13 SP1 updater blocks the download entirely unless the project is reconfigured for the new firmware. If the user forces a download anyway, the system data block is written with a configuration that the V4.2 firmware's HSC driver cannot interpret after a power cycle.
2. Cold-restart validation of the HSC descriptor. The first startup after download uses the freshly written configuration in volatile memory and the HSC may run momentarily. After a power-off/power-on, the configuration is read back from the CPU's load memory and the firmware validates the descriptor. The V4.0 descriptor layout is not bit-compatible with the V4.2 HSC configuration block, so validation fails and the CPU goes to STOP with the HSC HW_ID event.

This is consistent with Siemens' statement that V4.2 is replacement compatible only when the engineering project is rebuilt in a TIA Portal version that knows V4.2 (i.e., TIA V14 or later with the appropriate HSP).

Compatibility Matrix: TIA Portal vs. S7-1200 Firmware

Source: Siemens Support Entry 109741461 and the TIA Portal release notes.

Resolution Path A — Upgrade the Engineering Project to TIA V14

This is the supported, vendor-recommended path. The user who originally reported the issue confirmed: after switching the device in the project to firmware 4.2 inside TIA V14, the STOP fault on the V4.2 CPU disappeared.

Prerequisites

• Valid TIA Portal V14 license (or V14 SP1 for the latest HSP coverage of the 1214C).
• The latest Hardware Support Package (HSP) for V14 SP1 installed — this is what adds the 1214C V4.2 firmware variant to the device catalog.
• A backup of the V13 project (full TIA Portal project archive, not just the source files).

Step-by-step

1. Archive the V13 project. In TIA V13, choose Project → Archive… and save the .zap13 file. Confirm the archive contains the program blocks, PLC data types, hardware configuration, and the HSC setup under CPU Properties → High Speed Counters.
2. Install TIA V14 (or V14 SP1) on the engineering station. Do not uninstall V13 — Siemens supports side-by-side installation.
3. Install the latest HSP. Open TIA V14, choose Options → Support Packages, and import the HSP that contains the 6ES7 214-1AG40-0XB0 V4.2 device. Restart TIA if prompted.
4. Open the project in V14. TIA V14 will offer a project upgrade. Accept it. Review the upgrade log for warnings about blocks or system data that need to be re-compiled.
5. Re-select the device firmware. In the project tree, right-click the CPU 1214C DC/DC/DC, choose Change device / version…. Pick the 6ES7 214-1AG40-0XB0 entry whose Version column reads 4.2. Confirm with OK.
6. Re-validate HSC configuration. Open CPU Properties → High Speed Counters. For each enabled HSC (1, 2, …) verify:
   • Operating mode (Count, Period, Frequency, Motion) is still correct.
   • Address / input assignment matches the wiring (e.g., HSC 1 → I0.0 / I0.1).
   • Initial count value, reset value, and interrupt OB assignments are intact.
7. Compile the project (right-click the CPU → Compile → Software (rebuild all blocks)). Resolve any compile errors. TIA will report any HSC HW_ID remap; the displayed IDs may differ from V13 by a constant offset because the new firmware uses a different internal address table.
8. Download to the V4.2 CPU over the configured interface. The TIA download dialog should no longer show a firmware-mismatch warning.
9. Cycle power on the CPU. Verify it comes back in RUN and that HSC 1 / HSC 2 count events are still being captured in the configured interrupt OBs (e.g., OB40 for HSC 1 CV = PV interrupt).

Resolution Path B — Accept a Minor Firmware Revision Difference

If a V13 SP1 project must remain in V13 SP1 (e.g., a maintenance contract that forbids TIA upgrades), TIA Portal exposes a setting that lets the engineering tool download to a CPU whose firmware is a minor revision ahead of the project. This avoids the warning but does not fix the underlying descriptor mismatch that triggers the HSC STOP fault on a cold restart.

Where to set it

1. In TIA Portal, choose Options → Settings → Online & Diagnostics.
2. Open the page for the CPU family. Locate the checkbox "Accept minor firmware revisions when downloading" (exact label varies slightly between TIA versions and language packs).
3. Enable it. Click OK.

Resolution Path C — Downgrade the CPU to V4.0 (or V4.1)

If a V14 upgrade is not possible and the HSC STOP fault cannot be tolerated, the CPU can be flashed back to a V4.0 or V4.1 image. The V4.0 firmware file (or V4.1) must be obtained from Siemens' firmware download portal, which is the same portal Siemens lists in the firmware-release article (109741461).

Procedure (online firmware update via TIA)

1. Open the project in TIA V13 SP1 with the CPU 1214C configured as V4.0.
2. Go Online → Accessible devices, pick the V4.2 CPU.
3. Right-click the CPU in the project tree, choose Online & Diagnostics → Firmware update.
4. Select the V4.0 (or V4.1) firmware file from the local disk. Click Execute update.
5. Wait for the CPU to perform the internal flash programming. The CPU will restart automatically.
6. Re-download the project. Confirm the firmware in Online & Diagnostics → CPU information reads 4.0 (or 4.1).

Quick Decision Flow

HSC Configuration Quick-Reference (S7-1200 CPU 1214C)

When you rebuild the project in TIA V14 with the V4.2 device selected, the HSC properties panel changes only marginally. The following parameters must be checked before download.

For user program access, the standard block from the S7-1200 instruction palette is CTRL_HSC (or the extended variant CTRL_HSC_EXT introduced with V4.x firmware). Example invocation:

// In OB1 — cyclically called from the user program
// HSC 1 instance with HW_ID 257
// New count value: 1000
// No reset, no change of reference

"HSC_1_DB".CV_NEW    := 1000;
"HSC_1_DB".CV         := 16#0000;  // false: do not change CV
"HSC_1_DB".RV_NEW    := 0;
"HSC_1_DB".RV         := 16#0000;  // false: do not change RV
"HSC_1_DB".PERIOD    := 16#0000;  // false: keep current period
"HSC_1_DB".HSC       := 1;         // HSC number
"HSC_1_DB".DIR       := 16#0000;  // false: do not change direction

CTRL_HSC_1(EN := TRUE);

Verification Procedure

1. Go online. In TIA V14, click Go online. The status banner should read RUN, not STOP.
2. Check the diagnostic buffer. Online & Diagnostics → Diagnostics buffer. Confirm there are no HSC HW_ID events since the most recent power-on. The most recent entry should be a normal Restart (cold) event with a successful transition to RUN.
3. Force a power cycle. With the CPU in RUN, remove the 24 V supply for at least 5 seconds, restore it. The CPU must come back to RUN within ~5 seconds (typical for a 1214C with this I/O count). No STOP entry should appear in the diagnostic buffer.
4. Exercise the HSC input. Apply a known pulse train to the HSC input terminals (e.g., 1 kHz from a signal generator on I0.0 for HSC 1, counting mode = Count). Open a watch table on the HSC instance DB and verify the COUNT / CV value increments as expected.
5. Trigger the CV = PV interrupt. Set CV_NEW to a value that the next pulse will reach. Confirm OB40 fires (place a counter in OB40, or set a tag inside OB40 and watch it increment).
6. Repeat on at least one additional power cycle to rule out any warm-restart vs. cold-restart distinction. The original fault only manifested on the cold restart; verifying multiple cycles confirms the fix.

Troubleshooting Matrix

Preventive Measures for New Projects

• Pin the TIA Portal version in the project archive. When commissioning a V4.2 CPU, always open the project in TIA V14 (or later) and explicitly select V4.2 in the device properties. Document the firmware version in the project's cover page.
• Store HSC HW_IDs in a constants table. Avoid hard-coded numbers in user code. Use the constants table generated by TIA so that firmware upgrades that shift the address table are picked up automatically on recompile.
• Use CTRL_HSC_EXT (V4.x and later) rather than legacy CTRL_HSC where the application allows it. The extended block exposes the same parameters but is forward-compatible with V4.2 and V4.4 firmware revisions.
• Always perform a cold-restart test in the FAT/factory-acceptance procedure when the project uses any HSC, PTO, or PWM channel. The TIA download alone is not a sufficient verification — a power-cycle test is required.
• Maintain a firmware compatibility matrix in the maintenance documentation, listing the TIA Portal minimum version for each CPU firmware revision in service. This avoids the situation where a spare-parts replacement ships a newer firmware than the engineering tool knows about.

Notes on Other S7-1200 Modules in the Configuration

The communication board CB 1241 (RS485, 6ES7 241-1CH30-1XB0) and the analog module SM 1234 AI4/AQ2 (6ES7 234-4HE32-0XB0) were not implicated in the fault. Their firmware versions (V1.0 and V2.0 respectively) are unaffected by the CPU firmware V4.2 upgrade. After completing the TIA V14 project upgrade, both modules are picked up automatically by the V14 hardware catalog. No additional configuration changes are required on the CB or SM modules.

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