Page 10 Function-Decoders MX681, MX685, MX686, MX687, MX688
3.8 The NMRA-DCC function mapping
CVs #33 to #46
are reserved for the function mapping of the
first address
. It links a specific function
key to a specific function output. It is also possible to control several function outputs with one func-
tion key. Each function key is represented by a single CV in the in the table below. The individual bits
of a CV represent individual function outputs.
Due to the fact that function decoders have a maximum of 8 function outputs (headlights, FA1-FA6),
the "superfluous" bits (see table below) are shifted to the left (according to NMRA rules), so that "low"
function outputs (FA0v / r, FA1) can also be controlled by "high" function keys (F3 and higher).
Below:
NMRA standard bits (dark gray boxes) and “right shifted” bits (shaded gray):
N
M
R
A
F
un
c
ti
on
CV
Number key
on ZIMO
cabs
Function outputs;
FA6
FA5
FA4
FA3
FA2
FA1
Rear
light
Front
light
F0
#33
1 (L) fw
7
6
5
4
3
2
1
0
F0
#34
1 (L) re
7
6
5
4
3
2
1
0
F1
#35
2
7
6
5
4
3
2
1
0
F2
#36
3
7
6
5
4
3
2
1
0
F3
#37
4
4
3
2
1
0
7 6 5
F4
#38
5
4
3
1
0
7 6 5
F5
#39
6
4
3
2
1
0
7 6 5
F6
#40
7
4
3
2
1
0
7 6 5
F7
#41
8
1
0
7 6 5 4 3 2
F8
#42
9
1
0
7 6 5 4 3 2
F9
#43
0
1
0
7 6 5 4 3 2
F10
#44
1
1
0
7 6 5 4 3 2
F11
#45
2
1
0
7 6 5 4 3 2
F12
#46
3
1
0
7 6 5 4 3 2
The black dots in the table above indicate the default settings at the time of delivery, where each func-
tion key corresponds to the same numbered function output. Therefore, the following values were writ-
ten to these CV’s by default:
CV #33 = 1
CV #34 = 2
CV #35 = 4
CV #36 = 8
CV #37 = 2
CV #38 = 4
CV #39 = 8
CV #40 = 16
and so on
The
Function mapping for the
Second address
is defined (in the same way as for the first
address) with
CVs #69 to #82
The commands of the first and the second address are read separately, and stored according to the
respective "function mapping" and the desired function output states.
After power-on (system boot-up, longer track power interruption etc.), the decoder is first waiting for a
SECOND ADDRESS command (provided the second address is not 0) and the outputs are set based on
this secondary address command. (First-address commands are executed only if changes in the function
output states between successive first-address commands occur.) During continued operation the
"prin-
ciple of the most recent change"
between first and second address commands applies.
Identical to the first address
: NMRA standard bits (dark gray) and “right shifted” bits (shaded gray):
N
M
R
A
F
un
c
ti
on
CV
Number key
on ZIMO
cabs
Function outputs
Function outputs;
FA6
FA5
FA4
FA3
FA2
FA1
Rear
light
Front
light
F0
#69
1 (L) fw
7
6
5
4
3
2
1
0
F0
#70
1 (L) re
7
6
5
4
3
2
1
0
F1
#71
2
7
6
5
4
3
2
1
0
F2
#72
3
7
6
5
4
3
2
1
0
F3
#73
4
4
3
2
1
0
7 6 5
F4
#74
5
4
3
1
0
7 6 5
F5
#75
6
4
3
2
1
0
7 6 5
F6
#76
7
4
3
2
1
0
7 6 5
F7
#77
8
1
0
7 6 5 4 3 2
F8
#78
9
1
0
7 6 5 4 3 2
F9
#79
0
1
0
7 6 5 4 3 2
F10
#80
1
1
0
7 6 5 4 3 2
F11
#81
2
1
0
7 6 5 4 3 2
F12
#82
3
1
0
7 6 5 4 3 2
Tip: Directional taillights with the help of
special effect CV’s:
With the NMRA function mapping only F0 can be directional and was intended for the headlights, so
they automatically switch betwee
n “front” and “rear” when the driving direction is changed. All other
functions are controlled direction-independent.
The special effect CVs #125 - 132, #1
59 and #160 (see chapter “Special function output effects”),
each assigned to a function output (up to FO8), make it possible to have more direction dependent
functions. To utilize only the directional capabilities of these CVs use only the directional Bits 0 and/or
1 without setting the actual effect-bits.
