ZIMO MS / MN / FS Decoders — Configuration Reference

Reference documentation for ZIMO MS (sound), MN (non-sound), and FS (function-sound) decoder families. This document is not tied to the BigFred or Loco runtime; it is intended as a future data source for decoder configuration.

MS and MN decoders share the same hardware (except sound components) and software. Sections marked sound only can be ignored for MN decoders.

Acceleration, deceleration, and speed

Shunting mode

Output mapping, brightness, and lighting effects

Digital coupler (uncoupler)

Smoke generator

Volume regulation

C — Full CV table

1. Acceleration, deceleration, and speed

1.1 Basic momentum (CV #3 and CV #4)

The fundamental acceleration and deceleration times are set with CV #3 (acceleration) and CV #4 (deceleration), per NMRA convention:

Practical guidance:

• Use values 3 or higher for smooth driving; start with 5 for very slow starts/stops.
• Values above 30 are rarely useful except with the brake key.
• On sound decoders, the loaded sound project usually defines its own CV #3/#4 defaults. Changing them too far from the project values can break sound synchronisation.

Important difference from MX decoders: On MS/MN decoders, acceleration/deceleration follows the speed table (including interpolation), not 255 equidistant steps. An exponential speed curve therefore produces exponential acceleration behaviour. MX decoders needed CV #121/#122 for this; MS/MN do not.

CV #49 / #50 interaction (HLU/ABC): For signal-controlled operation, only the higher of CV #3 or CV #49 (acceleration) and CV #4 or CV #50 (deceleration) is used — values are not added (unlike MX decoders).

1.2 Temporary momentum variation (CV #23, #24)

1.3 Adaptive acceleration (CV #123) — SW 6.00+

1.4 Speed curve selection (CV #29, bit 4)

3-point speed curve

28-point speed curve

Directional speed trimming

1.5 Voltage reference and motor regulation (CV #57, #58, #9, #56, #147–#149)

CV #57 — Voltage reference

Specifies the reference voltage for motor regulation. The decoder tries to deliver the exact fraction of this voltage to the motor regardless of track voltage fluctuations.

CV #58 — BEMF / load compensation intensity

Useful range: 100–200. Locomotives in consists should never run at 100% compensation across the full speed range — this causes fighting and derailments.

For precise load compensation across the full range, use CV #58 together with CV #113 (3-point curve). Note: CV #10 on MX decoders; on MS decoders CV #10 serves another function.

Motor control PID (CV #9, #56, #147–#149)

Recommended starting values by motor type:

Tuning procedure for CV #56: Start at 11; drive slowly into an obstacle. Regulation should compensate within 0.5 s — if not, increase ones digit (12, 13, …). Then increase tens digit (23, 33, …) until judder appears, then step back.

CV #146 — Gear backlash compensation

Compensates for gear backlash on direction changes. Motor turns at minimum speed (CV #2) for a set duration before accelerating.

Only useful with CV #58 = 200–255. CV #2 must be set so the train moves correctly at step 1.

1.6 Motor brake (CV #151) — SW 6.00+

Useful for non-worm-gear locomotives to prevent rolling on grades.

1.7 Brake key (CV #309, #349)

1.8 Emergency stop (CV #111)

1.9 Distance-controlled stopping (CV #140, #141, #830–#833)

Alternative to time-controlled braking (CV #4):

Variant 1 (CV #140 = 1, 2, 3): At lower entry speed, train continues briefly then brakes normally — recommended.

Variant 2 (CV #140 = 11, 12, 13): Immediate braking even at low entry speed.

1.10 Signal-controlled speed influence (HLU / ABC)

Signal-controlled times in CV #49/#50 are added to CV #3/#4/#121/#122 curves and can only be equal or slower, never faster.

1.11 Analog operation speed (CV #14, #179)

1.12 Advanced / planned features (SW 6.00 preview)

2. Shunting mode

Shunting (manoeuvring) support allows temporarily reducing acceleration/braking times and limiting the speed range — essential when the prototypical momentum from CV #3/#4 is a hindrance during yard work.

2.1 Primary configuration — CV #124

Bit assignments in CV #124 (only when CV #155 = 0 and CV #156 = 0):

Acceleration deactivation type (bits 1, 0 — always apply, including with CV #155/#156):

Examples:

2.2 Extended half-speed key — CV #155 (preferred for new projects)

Alternative to CV #124 bit selections for half-speed:

Half-speed multiplier (bits 7, 6, 5 of CV #155):

2.3 Extended acceleration deactivation key — CV #156 (preferred for new projects)

Alternative to CV #124 for acceleration deactivation key selection:

The type of deactivation (bits 1,0 of CV #124) still applies when CV #156 selects the key.

2.4 MAN function — CV #157

Originally designed for ZIMO HLU; expanded to include Lenz ABC asymmetrical DCC signal stops.

2.5 Interaction rules

• If CV #155 > 0, any half-speed assignment in CV #124 is ineffective.
• If CV #156 > 0, any acceleration deactivation key assignment in CV #124 is ineffective.
• Bits 2, 3, 4, 6 in CV #124 (shunt key function selection) only apply when CV #155 = 0 and CV #156 = 0.
• Bits 0, 1 (deactivation type) always apply regardless of CV #155/#156.

2.6 Sound-related shunting features (sound decoders)

3. Output mapping, brightness, and lighting effects

ZIMO small-scale decoders provide 4–12 function outputs (FO). Large-scale decoders provide more. Consumers (lights, smoke, couplers, etc.) connect to FO1–FO8 (and beyond on large decoders).

3.1 NMRA function mapping (CV #33–#46)

Standard NMRA mapping: each function key (F0–F12) has one 8-bit register selecting which outputs it controls.

Each bit in the CV corresponds to one FO (bit 0 = FO1, bit 1 = FO2, …). Factory default: Fn controls FOn.

Limitations: Only 8 outputs per function key; only F0 is direction-dependent in standard NMRA mapping.

Example remapping (F2 also switches FO4; F3/F4 switch FO7/FO8 for couplers):

CV #36 = 40   (F2 → FO4 + FO6)
CV #37 = 32   (F3 → FO6)
CV #38 = 64   (F4 → FO7)

Extended NMRA mapping (CV #61)

3.2 Input mapping (CV #400–#428)

Remaps external function keys to internal decoder functions without changing sound projects:

3.3 Swiss mapping (CV #430–#507, #800–#823)

Complex function mapping for multi-state locomotive lighting (Swiss prototype, also useful elsewhere). 17 CV groups × 6 CVs = 102 CVs.

Each group structure:

Special M-key value CV #431 = 255: Full-beam override — outputs at full intensity via normal mapping, dimmed per CV #60 otherwise.

Dimming CVs #508–#512: Five dimming levels (0 = dark, 31 = full). Selected per group via bits 5–7 in A1/A2 CVs.

Speed-dependent high beam (CV #399): From SW 6.00. High beam only above configured internal speed step (Rule 17).

3.4 Global brightness / PWM dimming (CV #60, #114, #152)

Connection notes:

• Bulbs rated 12 V or higher can be dimmed via PWM even at high track voltage.
• Bulbs below 12 V (5 V, 1.2 V) must use the decoder's stabilised low-voltage pin, not PWM dimming.
• LEDs always need a series resistor; if resistor drops to 5 V, PWM dimming works (e.g. CV #60 = 50 for 25 V track).

Alternative dimming via low-voltage pin: Connect positive side to the decoder's stabilised low-voltage supply (see installation chapter) for constant voltage regardless of track voltage.

3.5 Low / high beam (CV #119, #120)

Example: CV #119 = 131 → headlights switch between high/low beam with F6.

3.6 Second dimming value (CV #115)

If more outputs need individual dimming than CV #60 allows, and uncoupler is not needed:

Configure the output's effect CV (#127–#132, #159, #160) as uncoupler (effect code 48), then use CV #115 ones digit for PWM reduction (0–90%). Hundreds digit sets wait time before driving away (if used as uncoupler).

3.7 Light suppression (CV #107, #108, #109, #110)

3.8 Direction-dependent outputs via effect CVs

Since NMRA mapping only makes F0 directional, use effect CVs with effect code 000000xx (direction only, no effect) for direction-dependent FO control.

Example 1 — directional taillights on F1:

CV #35 = 12   (F1 → FO1 + FO2)
CV #127 = 1   (FO1: forward only)
CV #128 = 2   (FO2: reverse only)

Example 2 — unilateral light suppression:

CV #33 = 1, CV #34 = 8
CV #35 = 6
CV #126 = 1, CV #127 = 2

3.9 Special lighting effects (CV #125–#132, #159, #160, #195–#200, #205–#207)

Each effect CV = 6-bit effect code (bits 7–2) + 2-bit direction code (bits 1–0):

Effect code table

Effect CV assignment by output

Effect modification CVs

Ditch lights: Only active when headlights (F0) and F2 are on (American prototype). CV #33/#34 bits must also enable the FO — effect CV alone is insufficient.

3.10 SUSI pins as additional outputs (CV #124 bit 7, #201, #203)

First non-zero CV in order (#201, #202, #203, #204, #181–#184) determines the application.

4. Digital coupler (uncoupler)

4.1 Effect assignment

Assign effect code 001100xx (48, 49, 50) to the function output driving the coupler solenoid:

Direction bits: 00 = both directions; 01 = forward; 10 = reverse.

4.2 Control CVs

CV #115 pull-in time (tens digit):

CV #115 hundreds digit — wait before driving away:

4.3 Recommended settings

Krois system: CV #115 = 60, 70, or 80 (2, 3, or 4 s pull-in at full track power).

Roco system: CV #115 can define hold-in voltage via ones digit (partial voltage during pull-in).

4.4 Automated uncoupling sequence

Automatic train disengagement is active when the tens digit of CV #116 ≠ 0.

Coupler unloading (optional): CV #116 > 100 — engine moves toward train to relieve coupler tension before uncoupling.

Procedure:

1. Uncoupling starts when the coupling function is activated and the train is at speed 0. If moving, the sequence waits for a full stop.
2. Coupler unloading and/or disengagement run for the times set in CV #115 (coupler) and CV #116 (disengagement).
3. Sequence ends when the function key is released (or pressed again in latched mode), or when times expire.
4. Aborted immediately if the throttle is moved during the sequence.
5. Disengagement direction follows the set direction; directional bits in the uncoupler effect CV are not applied.

Example:

CV #115 = 60   (2 s disengagement drive-away after uncouple)
CV #116 = 155  (active push to disengage, speed step 20, 1 s)

4.5 Wiring

Connect the uncoupler solenoid to any function output FO1–FO8 (or logic-level FO9+ via SUSI pin reconfiguration). The negative return connects to the decoder ground; positive to the FO pin (or via appropriate driver circuit per coupler manufacturer specifications).

For Krois/Roco digital couplers, follow the manufacturer's voltage and current ratings. The decoder FO outputs switch track voltage (or stabilised low voltage when connected to LV pin).

4.6 Worked example: PIKO SM31 PKP (MS450P22)

Field configuration for a PIKO SM31 with ZIMO MS450P22 (PluX22). The factory uses FO1 / FO2 (AUX1 / AUX2) for directional white and red lighting — do not assign the uncoupler there. On this model FO8 (cv41=128) drives shunting-step lighting; the digital coupler is wired to FO6 (AUX6, PluX pin 21).

F7 triggers uncoupling with:

• 2 s coupler energisation (CV #115)
• coupler unloading (push into the consist), then uncouple and drive away (CV #116 hundreds digit = 1)
• 5 s / speed step 28 for the automated move (CV #116 = 197)

Leave CV #127 / #128 at the PIKO project defaults (e.g. 89 / 90) so F0 and F4 lighting on FO1 / FO2 are unchanged.

loco cv set -l 31 "cv41=32, cv132=48, cv115=60, cv116=197, cv415=0, cv308=0"

CV #116 = 197 decodes as: hundreds 1 (push into consist first) · tens 9 (5 s) · ones 7 (7 × 4 = speed step 28). For a shorter or faster shove-away, try 167 (2 s, step 28) or 157 (1 s, step 28); see §4.2.

Sequence (loco at speed 0, direction set before F7):

1. Push into the consist (coupler unloading).
2. Uncouple (up to 2 s on FO6 per CV #115).
3. Drive away from the consist for the time set in CV #116.

The sequence aborts if the throttle is moved during the manoeuvre.

5. Smoke generator

5.1 Connection overview

Small / medium decoders (FO1–FO8)

Without fan (e.g. Seuthe 18 V):

• Heating element → any FO1–FO8.
• Configure effect code 72 (steam) or 80 (diesel) in the corresponding effect CV.

With fan (synchronised steam chuffs / diesel exhaust):

• Heating element → FO1–FO8 (with effect 72 or 80).
• Fan → FO4 (or FO2 on smaller decoders such as MS491). Set CV #133 = 1.
• Fan second pole: low voltage (5 V output if suitable) or external regulator.

Large-scale decoders (MS950, MS990, MN950)

Dedicated fan outputs V1 and V2 (5 V, ground-referenced) — strongly preferred over FO4 for fans:

ZIMO smoke generators:

Heating element voltage: 20–24 V. RAUSI/RAUDU units include overtemperature protection electronics; the decoder drives heaters and fans directly.

Wiring (dual RAUDU):

FO7 — common positive — FO3 — Ventilator V1 — GROUND — Ventilator V2

Use LOKPL950K / LOKPL990 adapter boards for plug-in connection.

5.2 Effect codes for smoke

Assign to effect CV for the FO carrying the heater. CV #137–#139 must be programmed or no smoke is produced.

5.3 Smoke characteristic (CV #137–#139)

Valid when effect 72 or 80 is assigned in CV #127–#132:

Example (Seuthe 18 V, ~20 V track):

CV #137 = 70–90    (little smoke at standstill)
CV #138 = 200      (~80% capacity from step 1)
CV #139 = 255      (maximum under acceleration → thick smoke)

5.4 Fan control

CV #133 — FO4 as fan output

Also configures reed input polarity (bits 2–6) and MS440: IN4 → FO9.

Fan speed CVs (V1)

Fan speed CVs (steam)

Dual smoke generators

When two heaters on different FOs both have effect 72/80: - Lower FO number → fan V1 automatically. - Higher FO number → fan V2 automatically. - V2 settings: CV page 145/0 (CV #31 = 145, CV #32 = 0), CV #500–#511 (planned SW 6).

Large-scale example (dual RAUDU on FO3 + FO7):

CV #159 = 72, CV #160 = 72   (steam, both heaters)
#430 = 6 (F6), #432 = 3 (FO3)
#436 = 7 (F7), #438 = 7 (FO7)

5.5 Overheat protection (CV #353)

After auto turn-off, function key must be pressed to reactivate smoke.

5.6 SUSI smoke generator (effect 76)

Connect SUSI smoke module via SUSI pins (default). Configure effect code 76 on the assigned FO.

5.7 SW 6.00 planned additions

• CV page 145/0 for fan V2 (#351, #352, #355 equivalents)
• Separate effect codes 116, 120, 124, 128, 132, 136 for split heater/fan control
• CV #394 bit 3: deactivate 2nd smoke fan and heating with solo-drive key (diesel dual-engine)

6. Volume regulation

This section applies to MS and FS sound decoders only.

Default volume values are defined by the loaded sound project, not the decoder firmware. A hard reset (CV #8 = 8) restores project defaults.

6.1 Master volume

6.2 Volume keys (CV #395–#397)

6.3 Driving sound on/off and fade (CV #310–#314)

6.4 Driving sound volume (CV #376)

6.5 Per-class background / driving sound volumes

Volume scale for all: 0 = full (same as 255); 1–254 = reduced 1–99.5%; 255 = full.

6.6 Per-function-key sound volumes

Each CV: 0–255. 0 or 255 = full volume; 1–254 = 1–99.5% of sample volume.

Adjacent CVs (e.g. #570, #572, #513, #515) store sound sample numbers and loop parameters — modifiable via CV #300 procedure.

6.7 Load-dependent chuff volume (steam)

Based on EMF measurements. Calibrate "basic load" first:

Requirements: Clear straight track (20 cm – 2 m depending on gauge), no grades/curves. Do not use roller test bench.

6.8 Brake squeal volume (CV #287, #288)

Brake squeal can also be assigned to a function key via CV #300 procedure (manual start/stop from SW 6.00).

6.9 Random and switch-input sound volumes

6.10 Sound equalising

ZIMO provides a sound equalising feature (see manual chapter 5) for adjusting frequency response. Refer to the factory manual for equaliser CV details and the CV #300 pseudo-programming workflow for sound sample selection.

Appendix A — MS decoder types (overview)

For pin-outs, current ratings, and wiring diagrams, see chapter 2 (Technical Data) and chapter 7 (Installation) in the factory PDF.

Appendix B — Key differences from MX decoders

Appendix C — Full CV table

Source: manual CV overview (chapter 8, pp. 70–87), SW 5.27.14. Defaults for CV #3/#4 may be overridden by the loaded sound project. FO effect codes: CV #125–#132 / #159–#160 — see §3.

CV #1–#31 — Address, consist, and configuration

CV #32–#66 — Function mapping, speed curve, and motor

CV #67–#124 — Speed table, Back-EMF, and braking

CV #125–#215 — Outputs, lighting effects, uncoupler, smoke

CV #216–#299 — Sound control and programming assist

CV #300–#399 — Sound samples, cam sensor, and smoke fan

CV #400–#499 — Indexed outputs and extended mapping

CV #500–#699 — Per-function sound volumes and samples

CV #700–#849 — Random sounds, RailCom, and version info

CV #850–#1024 — Extended / read-only

Document compiled from ZIMO instruction manual MS-MN-Decoders_EN.pdf, SW 5.27.14. Features marked SW 6.00 are preview/planned and may not be available in current firmware.