Resolving Sinumerik Alarm 15110 REORG Before Cycle978 Call

1. Problem Overview

When a Siemens SINUMERIK 840D sl or SINUMERIK 828D controller executes the measuring cycle CYCLE978 from a user-defined subprogram, the NCK can raise:

Alarm 15110 — REORG not possible (Reorganisation of the block memory not possible)

The alarm is raised during preprocessing of the block that calls CYCLE978. The interpreter reaches the cycle line, the NCK attempts to reorganise its lookahead buffer, and the reorganisation fails because the block contains variables whose values have not yet been resolved to a single, valid execution-time representation.

The fault blocks the program; no measuring motion is started, the probe is never deflected, and the operator sees the red alarm banner on HMI sl / SINUMERIK Operate.

2. Affected Systems and Firmware

The alarm applies to any measuring cycle that depends on synchronised settable frames or R-parameters evaluated by the cycle after a TRANS or frame write: CYCLE977, CYCLE978, CYCLE979, CYCLE982, CYCLE984 and customer OEM cycles that follow the same _KNUM / _PRNUM / _MVAR interface.

3. Anatomy of a CYCLE978 Call

The user program passes the work-table corner and probe coordinates through R-parameters and through the measurement system variables before the call. A minimal, representative block pattern looks like the example below. The numbering matches a typical N-numbered program where R5, R9 and R6 carry the work-table origin in X / Y / Z, R7 the measuring height, R34 the probing X-coordinate, and the system variables select the trigger event and probe.

;==================================================
; Measurement parameters
R5  = 40          ; Work-table origin X
R9  = 88.6/2      ; Work-table origin Y (half inner dimension)
R6  = 12          ; Work-table origin Z (web / part)
R7  = 24.4        ; Measuring height in Y
R34 = -50         ; Measuring point in X
;==================================================
N10  IF $P_SEARCH1==1 GOTOF Ohne
N20  G0 A2=0
N30  T99              ; Touch probe
N40  L26
N50  T1
N60  R8=R9-8
;---- Measure Z value 2:1 ----------------------------
N70  $P_UIFR[1,Z,FI]=0
N80  G17 G90 G54
N90  TRANS X=R5 Y=310 Z=0
N100 D1 M22           ; Probe monitoring ON
N110 TEST_D1_K2
N120 G0 X=R34 Y=0 Z=150 M5
N130 Z=75
N140 G1 Z=R6+10 F15000
N150 _CHBIT[0]=0      ; 1st measuring input
N160 _MVAR=100 _SETVAL=R6 _MA=3 _KNUM=1 _EVNUM=0
N170 _TSA=30 _PRNUM=2 _VMS=0 _NMSP=1 _FA=5
N180 CYCLE978         ; <<< Alarm 15110 raised here
N190 G0 Z150
N200 STOPRE
N210 R10=$P_UIFR[1,Z,FI]
N220 R41=R10
N230 STOPRE

The alarm fires during the preprocessing of block N180. Blocks N90 through N170 have written and read several variables that the interpreter must resolve before launching CYCLE978. The NCK prepares the next several blocks in its lookahead buffer so that contouring speed and look-ahead distance remain consistent; that preparation requires reorganisation of the buffer to recompute the order of motion blocks after the measuring cycle is inserted.

4. Root Cause: REORG and the Preprocessing Buffer

SINUMERIK interpreters pre-execute NC blocks up to a configurable depth (look-ahead) so that jerk-limited, look-ahead velocity profiling can be calculated. When a new block is inserted into the buffer — for example by a modal subprogram, an IF…GOTOF branch, a synchronous procedure call, or the substitution cycle loader — the buffer must be reorganised.

REORG can fail for three reasons relevant to a measuring cycle call:

1. Frame, R-parameter or system variable still pending write. $P_UIFR[1,Z,FI], TRANS, and the measurement system variables (_MVAR, _SETVAL, _KNUM, _TSA, _PRNUM, _VMS, _NMSP, _FA) all modify interpreter state. When the values for the next block are not yet committed, the reorganisation cannot continue and alarm 15110 is raised.
2. Modal subroutine or ASUB context active. A probe-monitoring routine such as TEST_D1_K2 runs in a modal context that holds an open reorganisation state.
3. Asynchronous subroutine (ASUB) start active. If the program was reached from an ASUB — for example a probe-deflection triggered start — the buffer is locked for reorganisation until the ASUB ends.

The fix is to commit all pending interpreter writes before the cycle call by inserting STOPRE.

5. Solution: Insert STOPRE Before the Cycle Call

The command STOPRE (Stop preprocessing, execute from here) flushes the NCK preprocessing buffer so that all preceding blocks are decoded and executed before the next block is processed. After STOPRE the buffer is empty, the state is consistent, and REORG can proceed.

Apply the fix by inserting a single STOPRE line immediately before CYCLE978:

N175 STOPRE            ; flush preprocessing buffer
N180 CYCLE978          ; measuring cycle, REORG now succeeds

The STOPRE takes effect on the next NC block after the cycle call as well — placing one immediately after the call (as the original program already did at N200) ensures the cycle's measured result is read consistently into $P_UIFR.

6. Verification Procedure

1. Select the program in Program Manager → Workpieces → NC Programs and load it to the NCK.
2. Switch to AUTO mode and confirm dry-run feed is enabled.
3. Single-block from N10 through N170; verify no alarm.
4. Single-block at N175; the channel status should show STOPRE active and the buffer pointer at the cycle line.
5. Run N180; the probe should approach the part, deflect, retract, and the measuring log should write one entry.
6. Run N200; verify $P_UIFR[1,Z,FI] returns a valid measurement.
7. Inspect Diagnostics → NC/PLC Variables for the value of $P_UIFR[1,Z,FI]; it must equal the actual deviation measured by the cycle.
8. Reset and run a full automatic execution; no alarm 15110 should appear.

7. Alarm 15110 Detail Sheet

The full Siemens alarm list is maintained in the SINUMERIK 840D sl / 828D / ONE Alarm List documentation (Siemens Industry Online Support).

8. Parameter and Variable Reference for CYCLE978

The cycle reads its inputs from a fixed set of NC system variables. When any of these are written in the same program section as the call, place a STOPRE immediately before CYCLE978.

9. Extended Pattern: Multiple Measuring Calls in One Program

When several measuring cycles run in sequence, STOPRE must be inserted before each call. A consolidated pattern for the original program is shown below.

;==================================================
; Measurement parameters
R5  = 40          ; Work-table origin X
R9  = 88.6/2      ; Work-table origin Y (half inner dimension)
R6  = 12          ; Work-table origin Z (web / part)
R7  = 24.4        ; Measuring height in Y
R34 = -50         ; Measuring point in X
;==================================================
N10  IF $P_SEARCH1==1 GOTOF Ohne
N20  G0 A2=0
N30  T99              ; Touch probe
N40  L26
N50  T1
N60  R8=R9-8
;---- Measure Z value 2:1 ----------------------------
N70  $P_UIFR[1,Z,FI]=0
N80  G17 G90 G54
N90  TRANS X=R5 Y=310 Z=0
N100 D1 M22           ; Probe monitoring ON
N110 TEST_D1_K2
N120 G0 X=R34 Y=0 Z=150 M5
N130 Z=75
N140 G1 Z=R6+10 F15000
N150 _CHBIT[0]=0
N160 _MVAR=100 _SETVAL=R6 _MA=3 _KNUM=1 _EVNUM=0
N170 _TSA=30 _PRNUM=2 _VMS=0 _NMSP=1 _FA=5
N175 STOPRE            ; <<< flush before cycle
N180 CYCLE978
N190 G0 Z150
N200 STOPRE            ; <<< flush after cycle, before frame read
N210 R10=$P_UIFR[1,Z,FI]
N220 R41=R10
N230 STOPRE

10. Related Alarms and Differences

11. Best-Practice Checklist for Measuring Programs

• Always assign R-parameters in one contiguous block at the top of the program; avoid scattering parameter writes between motion blocks.
• Insert STOPRE before any cycle that uses _KNUM, _PRNUM, _MVAR or _FA.
• Insert STOPRE after any cycle that writes a frame, before the frame is read back into R-parameters.
• Avoid IF…GOTOF jumps that skip a STOPRE in the same reorganisation window.
• Set _KNUM, _EVNUM, _PRNUM once at program start; do not change them between calls unless necessary.
• When using an ASUB for the probe-deflection trigger, make sure the ASUB returns via REPOS and not directly to the main program line.
• For OEM cycles that wrap CYCLE978, replicate the same STOPRE discipline around the wrap.

12. Edge Cases and OEM Variants

OEM cycles that call CYCLE978 internally. Many machine builders wrap CYCLE978 inside a manufacturer cycle (for example CYCLE_USER_MEAS) that sets _MVAR and _FA from machine data. The wrap still requires STOPRE on the calling side because the wrap itself can introduce additional reorganisation points.

ASUB-driven measurement. If the program reaches the measurement section through an asynchronous subroutine (for example after a soft-key Measure in the HMI), the ASUB must end with REPOS or the buffer remains locked. In this case STOPRE inside the calling program is not sufficient; the ASUB must be ended correctly first.

Synchronous actions. Synchronised actions with ID=... that read $P_UIFR while the measuring cycle is still writing can raise alarm 15110. Move the synchronous action into the cycle's idle phase, or guard it with a status flag that becomes true after the cycle's last block.

Multi-channel machines. If another channel modifies a global frame or system variable, REORG in the measuring channel can fail even when the local program is clean. Use channel-specific frames ($P_UIFR indexed by channel) where possible, and avoid cross-channel R-parameter writes during the measuring section.

13. Related Documentation

• SINUMERIK 840D sl / 828D Programming Manual (Basics)
• SINUMERIK Operate Programming Manual (Workpiece Measurement)
• SINUMERIK Alarm List (NCK Alarms)
• SINUMERIK Product Overview

Frequently Asked Questions