Configuring TPC-Jr G Series Digit Parameters for Fanuc 4th Axis

The setup is an add-on 4th/5th axis with its own drives and its own controller. On its parameter screen, each parameter shows eight positions. The manual says PCN (parameter No. 2, bit 4) can be0, 1, 2 or 3. When you try to key in a 2, the panel appears to accept only 0 or 1. The controller is fine. Those positions are not bits.

First check: confirm which parameter number and which column the cursor is on before you type anything. Most failed entries on this controller come from writing into the wrong position or the wrong parameter.

These parameters live in the axis controller, not in the Fanuc. The CNC parameter screen will never show PCN, CLPP or JPC. You edit them on the TPC-Jr panel with the machine stopped.

Skip the fixes that waste time on a digit-field parameter

These are the usual responses to a manual that lists values 0 to 3 for a single bit. None of them resolves the problem.

• Leave PCN and NLSC at 0 and move on. The factory default for the parameter is 00000000, so the machine will run. But 0 is one of four selectable behaviors for the P-mode switching level, not a neutral "off". Because JPC can make jog follow PCN, you have also fixed the jog behavior without choosing it.
• Treat it as a documentation typo and assume only 0/1 is valid. Parameter 103's recommended setting of 00000002 already contradicts that. So does the value 3 called for in CLPP 104#1. Many parameters in this manual assign values other than 0 and 1 to a single "bit".
• Pack the value as a binary or octal number. Some engineers try summing bit weights, switching the entry to octal, or typing one combined number for the whole parameter. This controller does not decode a packed word. Each position stores its own value.
• Look for a companion BCD parameter that holds the "real" value. None is needed. The value sits in the position itself.
• Dig through parameters 135 and 136. They hold the timings and forces used in P mode. They do not select the switching level that PCN controls.

Understand why eight "bits" each accept 0-9

The TPC-Jr G Series manual says it directly: data from 0 to 9 is set for each position, b0 through b7. The eight-column bit layout is a display format only. Each column is a single decimal digit cell, not a binary flag.

• A parameter that is a true on/off switch simply uses 0 and 1 in its cell.
• A parameter like PCN uses the same cell as a small selector: 0, 1, 2 or 3, with each value meaning a different behavior.
• Calling the cell a "bit" in the parameter table is misleading. Functionally, each parameter is an array of eight single-digit settings, and each digit is really a nibble or byte.

The manufacturer borrowed the familiar CNC bit-parameter screen layout and packed more options into it. Once you read every column as "digit 0-9", the whole manual makes sense. That includes the other parameters that list non-binary values.

The panel does accept 2 and 3 in the correct position. On this installation, a later attempt wrote the value successfully. The earlier failure came from writing into the wrong segment or the wrong parameter, not from a controller limit.

Match the entry symptom to its cause

Map the recommended strings to digit positions

Before you type anything, write out the full target string. The layout below assumes the usual CNC convention: b7 is the leftmost column and b0 is the rightmost. Confirm this against the column header in the manual's parameter table.

The recommended setting for parameter 103, 00000002, reads cleanly under that convention: b0 = 2.

Position:     b7 b6 b5 b4 b3 b2 b1 b0
No. 103:       0  0  0  0  0  0  0  2   recommended setting, b0 = 2
No. 104:       x  x  x  x  x  x  3  x   CLPP (104#1) = 3
No. 2:         x  x  x  n  x  x  x  x   PCN (2#4) = n, where n = 0..3

x = keep whatever digit is already there

• Parameter 104, CLPP at #1: the 3 goes in the second column from the right. If the rest of 104 is still at default zeros, the string becomes 00000030.
• Parameter 2, PCN at #4: the value goes in the fifth column from the right. With the rest at default, PCN = 2 reads 00020000.
• Other columns in 2 and 104: these carry other functions, including NLSC and JPC, depending on the parameter. Never assume they are zero. Read them first.

Enter a multi-value digit on the axis controller panel

1. Stop the machine and bring the rotary axis to rest. The failed entry on this installation happened while the machine was running; the successful one happened after it stopped.
2. Record the current full 8-digit string for parameters 2, 103, 104, 135 and 136. This is your rollback.
3. Enable parameter writing using whatever method the TPC-Jr G Series manual specifies for your unit, such as a key, mode or protect setting.
4. Select the parameter number. Check the number on screen before you move the cursor. Landing on an adjacent parameter is the most common reason an entry "won't take".
5. Move the cursor to the target column, counting from b0 on the right. Count it twice.
6. Key in the single digit (for example 3 for CLPP) and press the controller's input key.
7. Read back the whole 8-digit string. Only the target column should have changed.
8. Check the parameter table for any note saying the setting takes effect only after power-off. If it has one, cycle the axis controller before testing.
9. Disable parameter writing again.

If a digit above 1 is still refused in a column where the manual lists values 0-3, go back to step 4. You are almost certainly in the wrong parameter.

Decide PCN, JPC, NLSC and 135/136 together

These settings are coupled. Changing one without the others gives motion that looks wrong even though every value was entered correctly.

Work in this order:

1. Choose the PCN value from the manual's notes for the P-mode switching level.
2. Set 135/136 to the timings and forces that suit that level.
3. Choose JPC.
4. Leave NLSC at default unless the notes tie it to your PCN choice.

Confirm the setting took and the axis behaves on the Fanuc side

A correct read-back on the panel is only half the check. Timing changes on the axis side show up on the Fanuc as late or missing completion signals.

1. Read-back: compare every changed parameter against the planned string, and every unchanged one against your recorded originals.
2. Power cycle: if any edited parameter is marked as effective after power-off, cycle the controller and read back again. This confirms the value was stored and not just displayed.
3. Jog test: jog the axis at low speed. If JPC follows PCN, the jog should show the new P-mode behavior. If JPC is disabled, jog should be unchanged.
4. Handshake timing: on the Fanuc side, watch whether the finish/complete signal from the axis controller now arrives later. If it does, the CNC may wait or alarm. Correct this with 135/136, not with PCN.
5. Record: log the final 8-digit strings next to the originals so the next technician does not have to decode the columns again.

FAQ