S-9.2.2 Configuration Variables For Digital Command Control

Original (Wayback Machine)

Original Version: July 2012

This Standard provides a map and descriptions for Digital Decoder Configuration Variables. Configuration Variables allow the decoder to be customized for each locomotive, or other mobile or stationary devices. Unless otherwise specified, configuration Variables shall be stored in non-volatile memory and must not change when power is removed from the decoder over long extended periods of time.

A: General Definitions

Tables 1 and 2 identify each of the Configuration Variables (CVs), along with additional information about each one. Following Table 1 is a written description of each of the CVs. In Tables 1 and 2 each Configuration Variable (CV) is identified by name and number, along with the following information:

Required

Mandatory (M), Recommended (R) or Optional (O). CVs identified as Mandatory (M) must be implemented in order to conform to this Standard, while those marked as Recommended (R) are strongly encouraged but not mandatory, and those marked Optional (O) are at the manufacturer’s discretion.

Default Value

the required factory default value when the CV is provided in an implementation.

Read-Only

indicates a CV whose value should be set by the manufacturer and which the user cannot modify.

Uniform Spec

Many CVs are implementation specific and no uniform specification is required. Others must be implemented in a uniform fashion in order to achieve compatibility. A “Y” in the Uniform Spec column indicates a CV which requires implementation by manufacturers according to a common specification. A blank in the Uniform Specification means that the CV must be used for its designated purpose, but the action taken by the decoder for a specific value can vary from manufacturer to manufacturer.

Dynamic

CVs in this range are dynamic and are used for Unsolicited Decoder Initiated Transmission. Manufacturers who utilize these CVs are requested to contact the NMRA DCC WG for current uniform specifications.

Additional Comments

CVs identified as “Reserved by NMRA for future use” are allocated for future needs and must not be used by an implementer without prior written approval from the NMRA Technical Department. CVs identified as “Values assigned by NMRA” indicate that the allowable values are defined by the NMRA and any requests for additional values should be directed to the NMRA Technical Department. CVs identified as “Reserved for manufacturer use” are allocated for use by implementers, for which no prior NMRA authorization is needed, and for which no common usage across decoders from different implementers can be assured by the NMRA.

Note

While all Digital Decoders need not implement all variables, it is required that if a function is provided, that the all of the relevant CV information be adhered to.

Table 1: Multi-function Decoder Configuration Variables

CV Name	CV #	Required	Default Value	Read Only	Uniform Spec	Dynamic (Volatile)	Additional Comments
Primary Address	1	M	3		Y
Vstart	2	R
Acceleration Rate	3	R
Deceleration Rate	4	R
Vhigh	5	O
Vmid	6	O
Manufacturer Version No.	7	M		Y			Manufacturer defined version info
Manufacturer ID	8	M		Y	Y		Values assigned by NMRA
Total PWM Period	9	O
EMF Feedback Cutout	10	O
Packet Time-Out Value	11	R
Power Source Conversion	12	O			Y		Values assigned by NMRA
Alternative Mode Function Status F1-F8	13	O			Y
Alternative Mode Function Status FL, F9-F12	14	O			Y
Decoder Lock	15-16	O			Y
Extended Address	17+18	O			Y
Consist Address	19 20	O			Y		Reserved by NMRA for future use
Consist Address Active for F1-F8	21	O			Y
Consist Address Active for FL, F9-F12	22	O			Y
Acceleration Adjustment	23	O			Y
Deceleration Adjustment	24	O			Y
Speed Table / Mid-range Cab Speed Step	25 26	O			Y		Reserved by NMRA for future use
Decoder Automatic Stopping Configuration	27	O			Y		Under re-evaluation — see details
Bi-Directional Communication Configuration	28	O			Y		Under re-evaluation — see details
Configuration Data #1	29	M [1]			Y
Error Information	30	O			Y
Index High Byte	31	O			Y		Primary index for CV 257-512 00000000-00001111 Reserved by NMRA for future use
Index Low Byte	32	O			Y		Secondary index for CV 257-512
Output Location FL (f), FL (r), F1-F12	33-46	O			Y
Manufacturer Unique	47-64	O
Kick Start	65	O
Forward Trim	66	O
Speed Table	67-94	O
Reverse Trim	95 96-104	O					Reserved by NMRA for future use
User Identification #1	105	O					Reserved for customer use
User Identification #2	106	O					Reserved for customer use
Expanded Manufacturer ID	107-108						Reserved by NMRA for future use
Expanded CV 7	109-111						Reserved by NMRA for future use
Manufacturer Unique	112-256	O					Reserved for manufacturer use
Indexed Area	257-512 513-879 880-891					Y	See CV 31, 32. Index values of 0-4095 reserved by NMRA Reserved for manufacturer use Reserved for manufacturer use
Decoder Load	892	O			Y	Y
Dynamic Flags	893	O			Y	Y
Fuel/Coal	894	O			Y	Y
Water	895	O			Y	Y
SUSI Sound and Function Modules	896-1024	O			Y		See TN-9.2.3

Binary numerical quantities are stored such that the rightmost bit is the least significant, and the leftmost is the most significant.

Descriptions of Configuration Variables for Multi-Function Decoders

Configuration Variable 1: Primary Address

Bits 0-6 contain an address with a value between 1 and 127. Bit seven must have a value of 0. If the value of Configuration Variable 1 is 00000000 then the decoder will go out of NMRA digital mode and convert to the alternate power source as defined by Configuration Variable 12. This setting will not affect the Digital Decoder’s ability to respond to service mode packets (see S 9.2.3). The default value for this Configuration Variable is 3, if the decoder is not installed in a locomotive or other unit when shipped from the manufacturer.

Configuration Variable 2: V_start

V_start is used to define the voltage drive level used as the start voltage on the motor. The voltage drive levels shall correspond linearly to the voltage applied to the motor at speed step one, as a fraction of available rectified supply voltage. When the voltage drive level is equal to zero, there shall be zero voltage applied to the motor. When it is at maximum 11111111, the full available rectified voltage shall be applied.

Configuration Variable 3: Acceleration Rate

Determines the decoder’s acceleration rate. The formula for the acceleration rate \(a\) shall be equal to:

\[a = n \times 0.896 / s,\]

where \(n\) is the contents of CV 3 and \(s\) is the number of speed steps in use. For example, if the contents of CV 3 = 2, then the acceleration is 0.064 sec/step for a decoder currently using 28 speed steps. If the content of this parameter equals 0 then there is no programmed momentum during acceleration.

Configuration Variable 4: Deceleration Rate

Determines a decoders braking rate, in the same fashion as acceleration above (CV 3).

Configuration Variable 5: V_high

V_high is used to specify the motor voltage drive levels at the maximum speed step. This value shall be specified as a fraction of available rectified supply voltage. When the contents of CV 5 equal 11111111, the full available rectified voltage shall be applied. Values of 00000000 or 00000001 shall indicate that V_high is not used in the calculation of the speed table.

Configuration Variable 6: V_mid

V_mid specifies the voltage drive level at the middle speed step. V_mid is used to generate a performance curve in the decoder that translate speed step values into motor voltage drive levels and is specified as a fraction of available rectified supply voltage. Values of 00000000 or 00000001 shall indicate that V_mid is not used in the calculation of the speed table.

Configuration Variable 7: Manufacturer Version No.

This is reserved for the manufacturer to store information regarding the version of the decoder.

Configuration Variable 8: Manufacturer ID

CV 8 shall contain the NMRA assigned id number of the manufacturer of this decoder. The currently assigned manufacturer ID codes are listed in Appendix A of this Standard. The use of a value not assigned by the NMRA shall immediately cause the decoder to not be in conformance to this Standard. The CV shall be implemented as a read-only value, which cannot be modified.

Configuration Variable 9: Total PWM Period

The value of CV 9 sets the nominal PWM period at the decoder output and therefore the frequency is proportional to the reciprocal of the value. The recommend formula for PWM period should be:

\[p = (131 + m \times 4) \times 2e,\]

where \(p\) is PWM period in μs, \(m\) is a mantissa in bits 0-4 bits of CV 9 (low order) and \(e\) is an exp in bits 5-7 for CV 9. If the value programmed into CV 9 falls outside a decoder’s capability, it is suggested (but not required) that the decoder “adjust” the value to the appropriate highest or lowest setting supported by the decoder.

Configuration Variable 10: EMF Feedback Cutout

Contains a value between 1 and 128 that indicates the speed step above which the back EMF motor control cuts off. When 14 or 28 speed steps are used the LSB’s of the value are truncated appropriately.

Configuration Variable 11: Packet Time-Out Value

Contains the maximum time period that the decoder will maintain its speed without receiving a valid packet. See S 9.2.4 Section C for further information.

Configuration Variable 12: Power Source Conversion [2]

Contains the identity of the alternate power source to which the decoder will be converted should CV 1 contain all zeros. This is also the primary alternative power source selected should the decoder perform power source conversion. The currently assigned Power Source Conversion codes are listed in Appendix B of this Standard.

Configuration Variable 13: Alternate Mode Function Status

Indicates the status of each function (F1 through F8) when the unit is operating in alternate power mode, which cannot control the functions. If a function can be controlled, then the corresponding bit is ignored. A value of 0 indicates the function is off, while a value of 1 indicates the function is on. Bit 0 corresponds to F1, while Bit 7 corresponds to F8.

Configuration Variable 14: Alternate Mode Function 2 Status

Indicates the status of each function (F9 through F12, and FL) when the unit is operating in alternate power mode, which cannot control the functions. If a function can be controlled, then the corresponding bit is ignored. A value of 0 indicates the function is off, while a value of 1 indicates the function is on. FL in the forward direction is controlled by bit 0, FL in the reverse direction is controlled by bit 1. Bit 2 corresponds to F9, while Bit 5 corresponds to F12.

Configuration Variables 15, 16: Decoder Lock

The Decoder Lock is used to change CVs in only one of several decoders with the same short address (CV 1) or long address (CV 17 and CV 18) that are installed in the same locomotive. Assign a number to CV 16 in each decoder (i.e. 1 to motor decoder, 2 to sound decoder, 3 or higher to other decoders) before the decoders are installed in the locomotive. To change a value in another CV of one of the installed decoders, first write the number 1 (motor), 2 (sound), or 3 or higher (other) into CV 15, then send the new value to the CV to be changed. The decoders will compare CV 15 to CV 16 and, if the values are equal, the CV to be changed will be changed. If the values in CV 15 and CV 16 are different, the update will be ignored.

Configuration Variables 17, 18: Extended Address

The Extended Address is the locomotives address when the decoder is set up for extended addressing (indicated by a value of 1 in bit location 5 of CV 29). CV 17 contains the most significant bits of the two byte address and must have a value between 11000000 and 11100111, inclusive, in order for this two byte address to be valid. CV 18 contains the least significant bits of the address and may contain any value.

Configuration Variable 19: Consist Address

Contains a seven bit address in bit positions 0-6. Bit 7 indicates the relative direction of this unit within a consist, with a value of 0 indicating normal direction, and a value of 1 indicating a direction opposite the unit’s normal direction. If the seven bit address in bits 0-6 is 0000000 the unit is not in a consist.

Configuration Variable 21: Consist Address Active for F1-F8

Defines for functions F1-F8 whether the function is controlled by the consist address. For each Bit a value of 1 indicates that the function will respond to instructions addressed to the consist address. A value of 0 indicates that the function will only respond to instructions addressed to the locomotive address. F1 is indicated by bit 0. F8 by bit 7.

Configuration Variable 22: Consist Address Active for FL and F9-F12

Defines for function FL whether the function is controlled by the consist address. For each Bit a value of 1 indicates that the function will respond to instructions addressed to the consist address. A value of 0 indicates that the function will only respond to instructions addressed to the locomotive address. FL in the forward direction is indicated by bit 0, FL in the reverse direction is controlled by bit 1. Bit 2 corresponds to F9, while Bit 5 corresponds to F12.

Configuration Variable 23: Acceleration Adjustment

This Configuration Variable contains additional acceleration rate information that is to be added to or subtracted from the base value contained in Configuration Variable 3 using the formula:

\[a \times 0.896 / s,\]

where \(a\) is the contents of CV 23, \(s\) is the number of speed steps in use. This is a 7 bit value (bits 0-6) with bit 7 being reserved for a sign bit (0 — add, 1 — subtract). In case of overflow the maximum acceleration rate shall be used. In case of underflow no acceleration shall be used. The expected use is for changing momentum to simulate differing train lengths/loads, most often when operating in a consist.

Configuration Variable 24: Deceleration Adjustment

This Configuration Variable contains additional braking rate information that is to be added to or subtracted from the base value contained in Configuration Variable 4 using the formula:

\[a \times 0.896 / s,\]

where \(a\) is the contents of CV 24, \(s\) is the number of speed steps in use. This is a 7 bit value (bits 0-6) with bit 7 being reserved for a sign bit (0 — add, 1 — subtract). In case of overflow the maximum deceleration rate shall be used. In case of underflow no deceleration shall be used. The expected use is for changing momentum to simulate differing train lengths/loads, most often when operating in a consist.

Configuration Variable 25: Speed Table/Mid Range Cab Speed Step

A value between 2 and 127 shall be used to indicate 1 of 126 factory preset speed tables. A value of 00000010 indicates that the curve shall be linear. A value between 128 and 154 defines the 28-speed step position (1-26) which will define where the mid range decoder speed value will be applied. In 14-speed mode the decoder will utilize this value divided by two. If the value in this variable is outside the range, the default mid cab speed of 14 (for 28 speed mode or 7 for 14 speed mode) shall be used as the mid speed value. Values of 00000000 or 00000001 shall indicate that this CV is not used in the calculation of the speed table.

Configuration Variable 27: Decoder Automatic Stopping Configuration

Used to configure which actions will cause the decoder to automatically stop.

Bit	Description
0	Enable/Disable Auto Stop in the presence of an asymmetrical DCC signal which is more positive on the right rail. 0 = Disabled, 1 = Enabled.
1	Enable/Disable Auto Stop in the presence of an asymmetrical DCC signal which is more positive on the left rail. 0 = Disabled, 1 = Enabled.
2	Enable/Disable Auto Stop in the presence of an Signal Controlled Influence cutout signal. 0 = Disabled, 1 = Enabled.
3	Reserved for future use
4	Enable/Disable Auto Stop in the presence of reverse polarity DC. 0 = Disabled, 1 = Enabled.
5	Enable/Disable Auto Stop in the presence forward polarity DC. 0 = Disabled, 1 = Enabled.
6-7	Reserved for future use.

Note

If the decoder does not support a feature contained in this table, it shall not allow the corresponding bit to be set improperly (i.e. the bit should always contain it’s default value).

Configuration Variable 28: Bi-Directional Communication Configuration

Used to configure decoder’s Bi-Directional communication characteristics when CV 29-Bit 3 is set.

Bit	Description
0	Enable/Disable Unsolicited Decoder Initiated Transmission. 0 = Disabled, 1 = Enabled.
1	Enable/Disable Initiated Broadcast Transmission using Asymmetrical DCC Signal. 0 = Disabled, 1 = Enabled.
2	Enable/Disable Initiated Broadcast Transmission using Signal Controlled Influence Signal. 0 = Disabled, 1 = Enabled.
3-5	Reserved for future use.
6-7	Flag Bits, Reserved for future use

Note

If the decoder does not support a feature contained in this table, it shall not allow the corresponding bit to be set improperly (i.e. the bit should always contain its default value).

Configuration Variable 29: Configurations Supported

Bit	Description
0	Locomotive Direction: 0 = Normal, 1 = Reversed. This bit controls the locomotive’s forward and backward direction in digital mode only. Directional sensitive functions, such as headlights (FL and FR), will also be reversed so that they line up with the locomotive’s new forward direction. See S-9.1.1 for more information.
1	FL location: 0 = bit 4 in Speed and Direction Instructions control FL, 1 = bit 4 in Function Group One Instruction controls FL. See S-9.2.1 for more information.
2	Power Source Conversion: 0 = NMRA Digital Only, 1 = Power Source Conversion Enabled, See CV 12 for more information,
3	Bi-Directional Communications: 0 = Bi-Directional Communications disabled, 1 = Bi-Directional Communications enabled. See S-9.3.2 for more information.
4	Speed Table: 0 = Speed Table set by configuration variables 2, 5, and 6, 1 = Speed Table set by configuration variables 66-95.
5	0 = One Byte Addressing, 1 = Two Byte Addressing (also known as extended addressing), See S 9.2.1 for more information.
6	Reserved for future use.
7	Accessory Decoder: 0 = Multifunction Decoder, 1 = Accessory Decoder (see CV 541 for a description of assignments for bits 0-6)

Note

If the decoder does not support a feature contained in this table, it shall not allow the corresponding bit to be set improperly (i.e. the bit should always contain its default value).

Configuration Variable 30: Error Information

In the case where the decoder has an error condition this Configuration Variable shall contain the error condition as specified by the manufacturer. A value of 0 indicates that no error has occurred.

Configuration Variables 31, 32: Index High Byte, Index Low Byte

The Indexed Address is the address of the indexed CV page when the decoder is set up for indexed CV operation. CV 31 contains the most significant bits of the two byte address and may have any value between 00010000 and 11111111 inclusive. Values of 00000000 thru 00001111 are reserved by the NMRA for future use (4096 indexed pages). CV 32 contains the least significant bits of the index address and may contain any value. This gives a total of 61,440 indexed pages, each with 256 bytes of CV data available to manufacturers.

Note

If the decoder does not support a feature contained in this table, it shall not allow the corresponding bit to be set improperly (i.e. the bit should always contain its default value).

Configuration Variables 33-46: Output Locations 1-14 for Functions FL (f), FL (r), and F1-F12

Contains a matrix indication of which function inputs control which Digital Decoder outputs. This allows the user to customize which outputs are controlled by which input commands. The outputs that Function FL (f) controls are indicated in CV 33, FL (r) in CV 34, F1 in CV 35, to F12 in CV 46. A value of 1 in each bit location indicates that the function controls that output. This allows a single function to control multiple outputs, or the same output to be controlled by multiple functions. CVs 33-37 control outputs 1-8. CVs 38-42 control outputs 4-11 CVs 43-46 control outputs 7-14. The defaults is that FL (f) controls output 1, FL (r) controls output 2, F1 controls output 3 to F12 controls output 14. The lowest numbered output is in the LSB of the CV, as shown in the table below.

Table 2: Output Position vs. CV (a ‘d’ indicates the default position)

CV	Description	14 (MSB)	13	12	11	10	9	8	7	6	5	4	3	2	1 (LSB)
33	Forward Headlight FL (f)	—	—	—	—	—	—								d
34	Reverse Headlight FL (r)	—	—	—	—	—	—							d
35	Function 1	—	—	—	—	—	—						d
36	Function 2	—	—	—	—	—	—					d
37	Function 3	—	—	—	—	—	—				d
38	Function 4	—	—	—						d			—	—	—
39	Function 5	—	—	—					d				—	—	—
40	Function 6	—	—	—				d					—	—	—
41	Function 7	—	—	—			d						—	—	—
42	Function 8	—	—	—		d							—	—	—
43	Function 9				d					—	—	—	—	—	—
44	Function 10			d						—	—	—	—	—	—
45	Function 11		d							—	—	—	—	—	—
46	Function 12	d								—	—	—	—	—	—

Configuration Variable 47-64: Manufacturer unique

Configuration Variable 65: Kick Start

Specifies the amount of extra Kick that will supplied to the motor when transitioning between stop and the first speed step.

Configuration Variable 66: Forward Trim

Specifies a scale factor by which a voltage drive level should be multiplied, when the controller is driving the unit in the forward direction. It is interpreted as \(n/128\). If the Forward Trim configuration variable contains a value of 0 then forward trim is not implemented.

Configuration Variables 67-94: Speed Table

The speed table is defined to be 28 bytes wide, consisting of 28 values for forward speeds. A digital controller that uses this table shall have at least 64 voltage drive levels and can have as many as 256 so that a smooth power curve can be constructed. Note that voltage drive levels are specified in integer values, in the same way as most other parameters. This means that a drive level of \(1/4\) maximum voltage corresponds to 0100000, not 0010000, as you would expect if the number specified a fraction with a fixed denominator, i.e. value 32 out of a fixed 128 levels (see Definitions section).

Configuration Variable 95: Reverse Trim

Specifies a scale factor by which a voltage drive level should be multiplied, when the controller is driving the unit in the reverse direction. It is interpreted as \(n/128\). If the Reverse Trim configuration variable contains a value of 0 then reverse trim is not implemented.

Configuration Variable 96-104: NMRA Reserved

Configuration Variable 105-106: User Identification #1 and #2

These CVs are reserved for use by the owner of the decoder to store identification information, e.g. NMRA membership number. CV 105 is ID #1 and CV 106 is ID #2.

Configuration Variable 107-111: NMRA Reserved

CVs 107, 108: with CV 8 = 0xEE, a 16-bit manufacturer ID is stored in these two CVs

CVs 109-111: with CV 7 = _________, these three CVs expand the version number feature.

Configuration Variable 112-256: Manufacturer Unique

CVs in this range are already being used by many manufacturers. Opening up this area officially is an attempt to legitimize what is already being done.

Configuration Variable 257-512: Indexed Access Area (see also CV 31, 32)

This is the indexed area. It contains a total of 65536 pages, each 256 bytes in length. The first 4096 pages are reserved for NMRA use. The remaining 61440 pages are available to manufacturers for their own purposes. For the manufacturer that needs only 256 additional bytes of CVs, he can simply specify a base address in CV 31-32 and not respond if that address is not enabled without actually paging data.

Configuration Variable 880-895: Dynamic CVs

CVs in this range are dynamic and are used for Unsolicited Decoder Initiated Transmission. Manufacturers who utilize these CVs are requested to contact the NMRA DCC WG for current uniform specifications.

Configuration Variable 892: Decoder Load

Specifies the current load of the decoder. The load is volatile and is not stored across power interruptions. Bits 0-6 indicate the value of the load with 0 indicating no load, Bit 7 indicates a positive or negative load.

Configuration Variable 893: Flags

Up to 8 dynamic flags can be transmitted. Bits 0-7 Reserved for future use.

Configuration Variable 894: Fuel/Coal

Specifies the amount of Fuel/Coal left before the decoder will stop the locomotive. A value of 0 indicates that the Fuel/Coal is totally consumed, a value of 254 indicates totally full and a value of 255 indicates that this CV is not currently supported and its contents should not be transmitted.

Configuration Variable 895: Water

Specifies the amount of water left before the decoder will stop the locomotive. A value of 0 indicates that the water is totally consumed, a value of 254 indicates totally full and a value of 255 indicates that this CV is not currently supported and its contents should not be transmitted.

Configuration Variable 896-1024: SUSI (Serial User Standard Interface)

Reserved until March 2005 for use by SUSI to define CVs for Sound and Function auxiliary modules. See Technical Note TI-9.2.3 for details.

Table 3: Accessory Decoder Configuration Variables

CV Name	CV #	CV # (Optional)	Required	Default Value	Read Only	Uniform Spec	Additional Comments
Decoder Address LSB	1	513	M	1		Y	6 LSB of accessory decoder address
Auxiliary Activation	2	514	O				Auxiliary activation of outputs
Time On F1	3	515	O
Time On F2	4	516	O
Time On F3	5	517	O
Time On F4	6	518	O
Manufacturer Version Info	7	519	M				Manufacturer defined version info
Manufacturer ID	8	520	M		Y	Y	Values assigned by NMRA
Decoder Address MSB	9	521	M	0		Y	3 MSB of accessory decoder address
Not in Use	10-27		—				Reserved by NMRA for future use
Bi-Directional Communication Configuration	28	540	O			Y
Accessory Decoder Configuration	29	541	M [1]			Y	Similar to CV 29 for accessory decoders
Not in Use	30		—				Reserved by NMRA for future use
Indexed Area Pointers	32, 32						Index High and Low Address
Manufacturer Unique	33-81		O				Reserved for manufacturer use
Not in Use	82-111		—				Reserved by NMRA for future use
Manufacturer Unique	112-128		O				Reserved for manufacturer use
Manufacturer Unique	129-256
Indexed Area	257-512						See CV 31, 32. Index address values of 0-4095 reserved by NMRA
Manufacturer Unique	513-895		O				Reserved for manufacturer use
Not in Use	896-1024						Reserved by NMRA for future use

Descriptions of Configuration Variables for Accessory Decoders

Previous version of this Standard established CVs 513-1024 to be used by accessory decoders. CVs 1-512 were reserved for NMRA use. However, many accessory decoders were sold that used CVs 1-512. This was done for various reasons, including in inability of some command stations to access CVs above 512. In recognition of many accessory decoders using the lower CVs and the desire to create more space for manufacturers, the CV definitions as previously defined have been moved from 513-1024 down to 1-512. Using the CVs 513-1024, as defined in Table 2, are optional. The manufacturer may use these upper CVs in any manner they see appropriate. These changes will allow existing accessory decoders to use CVs 513-1024 as previously defined.

Configuration Variable 1 [513]: Decoder Address (LSB)

Contains the low-order address bits for Accessory Decoders. The high-order address bits are stored in CV 9 [521]. Two types of Accessory Decoder addressing are supported: Decoder Address and Output Address. An accessory decoder must support one type, and optionally the other type. The type of decoder is specified in CV 29 [541], bit 6. Decoders using either type of addressing will respond to the same Accessory Decoder Control Packet when CV 1 [513] = 1 and CV 9 [521] = 0. The factory default value is 1. The type(s) of addressing supported must be clearly documented in the manual and on the packaging.

1. Decoder Address: Contains the six least significant bits of the accessory decoder’s address in bits 0-5. These bits are transmitted as bits 0-5 in the first byte of the accessory decoder packet. See S-9.2.1 for more information.

2. Output Address: Contains the address value results from the following formula:

\[a_o = a \mod 256,\]

where \(a_o\) is the Output Address, and \(a\) is the address.

The values contained in CV 1 [513] and CV 9 [521] correspond to the bits in the Accessory Decoder packets as follows:

\[o = (n_1 + n_9 \times 256) - 1,\]

where \(o\) is the Accessory Output, \(n_1\) is the value in CV 1 [513], and \(n_9\) is the value in CV 9 [521].

Bits 0 and 1 of the Accessory Output are transmitted as bits 1 and 2 of byte 2 of both Accessory Decoder Control Packets. Bits 2-7 of the Accessory Output are transmitted as bits 0-5 of byte 1 of both Accessory Decoder Control Packets. The three least-significant bits of CV 9 [521] contain the ones-complement of bits 4-6 of both Accessory Decoder Control Packets (See S-9.2.1 for more information on the Accessory Decoder Control Packets).

If an accessory decoder supports more than one sequential output the value in CV 1 [513] will be the first output in the series.

Configuration Variable 2 [514]: Auxiliary Activation

Bits 1-8 are Auxiliary activation, 0 output is not activated by an auxiliary input, 1 output can be activated by an auxiliary input.

Configuration Variables 3-6 [515-518]: Time On for Functions F1-F4

Functions F1-F4 can have the time the outputs are active set by Configuration Variables 3 [515] – 6 [518]. Configuration Variable 3 [515] controls Function F1 and Configuration Variable 6 [518] Controls Function F4. Contains a time that the output is on each time the state of the function is activated. A value of all 0s indicates continuous on.

Configuration Variable 7 [519]: Manufacturer Version Number

See CV 7 for the description.

Configuration Variable 8 [520]: Manufacturer ID (See Appendix A for a list of Manufacturer IDs)

See CV 8 for the description.

Configuration Variable 9 [521]: Decoder Address (MSB)

Contains the high-order address bits for Accessory Decoders. The low-order address bits are stored in CV 1 [513]. Two types of Accessory Decoder addressing are supported: Decoder Address and Output Address. An accessory decoder must support one type, and optionally the other type. The type of decoder is specified in CV 29 [541], bit 6. Decoders using either type of addressing will respond to the same Accessory Decoder Control Packet when CV1 [513] = 1 and CV9 [521] = 0. The type(s) of addressing supported must be clearly documented in the manual and on the packaging. The bits transmitted are the ones complement of the value in this CV. See S-9.2.1 for more information on the Accessory Decoder Control Packets.

1. Decoder Address: Contains the three most significant bits of the accessory decoder’s address in bits 0-2. These bits are transmitted as bits 4-6 in the second byte of the accessory decoder packet.

2. Output Address: Contains the address value results from the quotient of the following formula:

\[a_o = a / 256,\]

where \(a_o\) is the Output Address, and \(a\) is the address.

See CV 513 [1] for an explanation of how to determine the contents of CV 1 [513] and CV 9 [521].

Configuration Variable 28 [540]: Bi-Directional Communication Configuration

Used to configure decoder’s Bi-Directional communication characteristics, when CV 29 [541] bit 3 is set.

Bit	Description
0	Enable/Disable Unsolicited Decoder Initiated Transmission. 0 = Disabled, 1 = Enabled.
1	Not used.
2-5	Reserved for future use.
6-7	Flag Bits, Reserved for future use.

Note

If the decoder does not support a feature contained in this table, it shall not allow the corresponding bit to be set improperly (i.e. the bit should always contain its default value).

Configuration Variable 29 [541]: Accessory Decoder Configurations Supported

Bit	Description
0-2	Reserved for future use.
3	Bi-Directional Communications. See S-9.3.2 for more information. 0 = Disabled, 1 = Enabled.
4	Reserved for future use.
5	Decoder Type. 0 = Basic Accessory Decoder, 1 = Extended Accessory Decoder.
6	Addressing Method. 0 = Decoder Address method, 1 = Output Address method.
7	Accessory Decoder, 0 = Multifunction Decoder (See CV 29 for description of bit Assignments for bits 0-6), 1 = Accessory Decoder. If bit 7 = 1, then the decoder may ignore the two most-significant bits of the CV number in Service Mode only. Using this feature CV 513 becomes CV 1, etc. Decoders which perform the translation must clearly document the feature in their manual.

Note

If the decoder does not support a feature contained in this table, it must not allow the corresponding bit to be set improperly (i.e. the bit should always contain its default value).

Configuration Variable 31, 32: Index Address High Byte, Index Address Low Byte

The Indexed Address is the address of the indexed CV page when the decoder is set up for indexed CV operation. CV 31 contains the most significant bits of the two byte address and may have any value between 00010000 and 11111111 inclusive. Values of 00000000 through 00001111 are reserved by the NMRA for future use. (4096 indexed pages) CV 32 contains the least significant bits of the index address and may contain any value. This gives a total of 61,440 indexed pages, each with 256 bytes of CV data available to manufacturers.

Appendix A: Manufacturer ID codes as assigned by the NMRA

This appendix is published separately since it is under constant revision.

Appendix B: Power Source Conversion codes as assigned by the NMRA

The following Power Source Conversion codes have been assigned by the NMRA Technical Department. Manufacturers wishing to use conversions not on this list shall apply to the NMRA Technical Department for the assignment for a conversion ID.

ID	Description
00000001	Analog Power Conversion
00000010	Radio
00000100	Zero-1465
00001000	TRIX
00010000	CTC 16 / Railcommand
00100000	FMZ (Fleischmann)

Appendix C: Process for changing Manufacturer Specific CVs to Optional or Uniform

An official process whereby CVs incorporated initially as Manufacturer Specific options may be incorporated into the Standard for optional and/or uniform usage by all manufacturers needs to be defined and inserted here.

Footnotes

[1] (1,2)

If any of these features are provided, then this CV is Mandatory

[2]

Allocation of these bits is done by the NMRA on an as needed basis.