Working documentation
This page is generated from the project's working notes. It records a real retrofit in progress, corrections included. Anything marked 🔴 or ⚠️ is unresolved or carries a caveat - read those before acting.
SGDH drive reference — Pn000.1 and the CN1 pinout¶
Extracted 31 Aug 2026 from XYZ Axis yaskawa_sigma_II_manual.pdf (Drive ID 17wNFtjvOU5Q65fVuuYsop6vcGR2X1Heq), the Sigma II User's Manual.
⚠️ Scope of this extract: the text layer covered pages 1–131 only. Appendix B, which holds the complete switches table, sits beyond that and was not read. Everything below is marked for where it came from.
Pn000.1 — Control Method Selection¶
Confirmed from the manual: Pn000.1 is "Function Selection Basic Switches: Control Mode Selection", default setting 0.
Values confirmed directly in this manual¶
| Value | Meaning |
|---|---|
| 2 | Torque control (dedicated). Torque reference on T-REF (CN1-9) |
| 6 | Speed control (contact reference) ⇔ torque control. Switched by /P-CL (CN1-45) and /N-CL (CN1-46) |
| 8 | Position control ⇔ torque control. Switched by /P-CON (CN1-41) |
| 9 | Torque control ⇔ speed control (analog reference). V-REF gives speed, T-REF gives torque |
The two values that matter here — high confidence, not read directly¶
| Value | Meaning |
|---|---|
| 0 | Speed control (analog reference) → Option B, the 7I77 |
| 1 | Position control (pulse train reference) → Option A, the 7I76EU alone |
These come from the standard SGDH table rather than from the pages extracted. Confidence is high because all four values that were read (2, 6, 8, 9) match that standard table exactly, and because the manual's own cross-references are consistent with it — Pn200.0 sets the position reference pulse form, Pn202/Pn203 set the electronic gear, and Pn300 sets the speed reference gain. Worth a glance at Appendix B when someone has the full manual open, but do not hold up work for it.
⛔ Do not open or disturb the CN1 connectors (Grant, 31 Aug 2026)¶
The CN1 looms are professionally made, with 50-pin connectors and fine crimps. They are not to be opened, unplugged or probed to answer questions that can be answered another way. Disturbing a working servo connection on a healthy machine, to confirm something the drive panel or the drawing will tell you for free, is a bad trade.
Answer CN1 questions in this order:
1. Read the parameter on the drive's front panel - Pn000.1. Nothing unplugged, no covers off, definitive.
2. Read the wiring diagram - the AZIONAMENTO ASSE X/Y/Z sheets show the CN1 pin usage directly. They sit near the encoder sheets at 29-32.
3. Only if both fail, and with a specific reason, consider anything physical - and then plan it properly rather than opening a loom to look.
This also fits the retrofit boundary (CLAUDE.md §5.4): the drive end stays as built. Where the Tecnos is replaced, the change happens at the Tecnos end of that cable, not at the drive.
The pin groups, for reading off the drawing¶
The two candidate modes use different CN1 pins, so the drawing distinguishes them without any hardware being touched:
The two modes use different CN1 pins, so the connector answers the question independently of the parameter:
| If these are wired | Mode | Meaning |
|---|---|---|
CN1-5 and CN1-6 (V-REF, SG) |
Analog speed reference | Option B — 7I77 |
CN1-7, 8, 11, 12 (PULS, /PULS, SIGN, /SIGN) |
Position reference pulse train | Option A — 7I76EU alone |
The wiring diagram already shows REFERENCE and 0V against each drive's 1CN (see wiring-diagram-index.md), which is CN1-5/6 - consistent with analog speed reference. Confirm it from the drawing and the drive panel, not by opening the connector.
CN1 pinout — the pins this retrofit cares about¶
| Signal | Pin(s) | Function |
|---|---|---|
V-REF, SG |
1-5, 1-6 | Speed reference input (analog) and its ground |
T-REF, SG |
1-9, 1-10 | Torque reference input and ground |
PULS, /PULS, SIGN, /SIGN |
1-7, 1-8, 1-11, 1-12 | Position reference pulse train (step/direction) |
PAO, /PAO |
1-33, 1-34 | Encoder output, A phase (differential) |
PBO, /PBO |
1-35, 1-36 | Encoder output, B phase (differential) |
PCO, /PCO |
1-19, 1-20 | Encoder output, C phase / index (differential) |
SG |
1-1 | Signal ground |
PSO, /PSO |
1-48, 1-49 | Absolute encoder S phase (absolute encoders only) |
BAT(+), BAT(-) |
1-21, 1-50 | Absolute encoder battery |
SEN |
1-4 | Absolute encoder SEN signal |
/S-ON |
1-40 | Servo ON |
/P-CON (/C-SEL) |
1-41 | Control mode switching |
P-OT |
1-42 | Forward run prohibited (overtravel) |
N-OT |
1-43 | Reverse run prohibited (overtravel) |
CN2 (2CN) is the motor encoder input to the drive — PG5V/PG0V on 2-1/2-2, phases on 2-5/2-6 etc. This is what the wiring diagram's sheets 29–32 show. It is not a source of position for LinuxCNC.
What this means for the retrofit¶
If Pn000.1 reads 0 and Option B is chosen, LinuxCNC closes the position loop and needs the drive's encoder output, which is on CN1 pins 33/34, 35/36 and 19/20 — differential line-driver outputs, exactly what the Mesa 7I77's encoder inputs expect.
So the question is: are CN1-33/34/35/36/19/20 already wired to the Tecnos? Answer it from the wiring diagram, not by opening the loom. - If yes, the position feedback Mesa needs is already run and terminated — a large saving. - If no, three differential pairs per axis must be added at the drive end. Not difficult, but it is work and connector pins that should be planned for.
Related parameters worth knowing when the time comes: Pn201 sets the encoder output dividing ratio, Pn300 the speed reference input gain, Pn202/Pn203 the electronic gear ratio (only relevant under position control).
Reading the parameters out of the drives¶
5 September 2026. Added from the Sigma II manual's Chapters 4 and 5, read directly from the PDF on Drive.
⚠️ Read the parameters BEFORE experimenting with the panel¶
The drives hold the only record of how this machine was commissioned. The realistic way to lose it is not a fault — it is an accidental keypress on the panel.
The panel exposes three families:
| Prefix | What it is | |
|---|---|---|
Pn |
Parameters | What you want. Reading is harmless |
Un |
Monitor modes (Un000-Un00D) |
Live speed, torque and I/O state. Read-only, and useful later |
Fn |
Auxiliary functions (Fn000-Fn014) |
🔴 Stay out. These execute things — JOG operation, and on this drive family, parameter initialisation. One confirmed keypress in the wrong place wipes the settings you came to record |
So: capture first, explore second. Get all three drives photographed before anyone starts learning the interface.
What to read, per drive¶
| Parameter | Why |
|---|---|
Pn201 |
PG dividing ratio → the LinuxCNC encoder scale. The one that matters most |
Pn300 |
Speed reference input gain → the LinuxCNC analog output scale. The other one that matters most |
Pn000 |
.0 direction, .1 control mode. Confirms what the drawing already proved |
Pn100-Pn103 |
Loop gains. Record only — so a working machine can be restored |
Pn202, Pn203 |
Electronic gear. Only meaningful under position control, but record them |
Pn50A, Pn50B |
Input allocations. Confirms the drawing |
Pn50E, Pn50F |
Output allocations. Pn50F on Z tells you whether the brake is on SO2 as /BK |
Pn506, Pn507, Pn508 |
Z drive only. The brake timing |
🔴 What the two key numbers mean¶
Both read directly from the manual, so these are not inferences.
Pn300 — Speed Reference Input Adjustment Factor¶
"Range: 150 to 3000 × (0.01 V / rated motor speed)" "The default setting is adjusted so that a 6 V input is equivalent to the rated motor speed" "Pn300 = 600: This setting means that 6 V is equivalent to the rated motor speed."
So the value is hundredths of a volt at rated speed:
Pn300 |
Means |
|---|---|
| 600 | 6 V = rated speed (factory default) |
| 1000 | 10 V = rated speed |
| 300 | 3 V = rated speed |
⚠️ Maximum allowable input is ±12 V. The Mesa 7I77's ±10 V output is comfortably inside that.
Do not assume 600. A machine builder sets this to suit the controller, and the whole point of reading it is that the Tecnos may not have used the default.
Pn201 — PG Dividing Ratio¶
"Dividing means converting an input pulse train from the encoder mounted on the servomotor according to the preset pulse density and outputting the converted pulse. The units are pulses per revolution (PPR)." "The dividing ratio setting is not related to the gear ratio setting (Pn202 and 203)."
So Pn201 is pulses per motor revolution on the A/B/C outputs at CN1-33/34, 35/36, 19/20 — the differential pairs the 7I77 will read.
⚠️ PPR is not counts. LinuxCNC counts quadrature edges, so expect Pn201 × 4 counts per motor revolution before the ballscrew ratio is applied. That step is standard quadrature arithmetic, not something the manual states — confirm it against the measured axis scaling rather than trusting it alone.
This is why Pn201 and the axis scaling measurement (survey item 2) belong together: one gives counts per motor turn, the other gives millimetres per turn, and between them the LinuxCNC scale falls out.
⚠️ The gap: the key sequence is not in our copy of the manual¶
The PDF's text layer ends at page 131, part-way through Chapter 5. Every procedure reference points at Chapter 7 — 7.1.6 Operation in Parameter Setting Mode and 7.1.7 Operation in Monitor Mode — and Chapter 7 is beyond the readable text.
So the exact keypresses cannot be quoted from the machine's own documentation. Three ways forward, in order:
- Photograph the panel and the display, and work it out with the drive in front of you. The interface is four keys and the mode families above are known
- Find a complete Sigma II / SGDH manual with Chapter 7 and Appendix B. Appendix B is also the outstanding gap on the
Pn000.1value table - Yaskawa's own PC software over
CN3— needs the manufacturer's cable and software, and is not worth sourcing for a one-off read
How to record it¶
Photograph each parameter on the display. Do not transcribe by hand — a mis-copied digit in Pn201 or Pn300 is a machine that moves the wrong distance, and the error will not be obvious.
One photo per parameter, three drives, roughly 36 photos. Name them X-Pn201.jpg and so on, and get them into the repo. Transcribe from the photos afterwards, with the photos kept as the record.
⚠️ Reading changes nothing, and the manual confirms it indirectly: "Turn OFF power once after changing any parameter except Pn300. The change will not be valid until power is restored." If a value ever starts flashing or the display asks to confirm, back out without confirming.