SoundTraxx DSD-150/DSX Owners Manual User Manual
Page 26
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Digital Sound Decoder Owner's Manual
Table D.
Calculating the User Loadable Speed Table
CV #
Speed Step
% Full Speed
CV Value
CV 67
1
0
0 (0x00)
CV 68
2
4
9 (0x09)
CV 69
3
7
18 (0x12)
CV 70
4
11
28 (0x1C)
CV 71
5
15
37 (0x25)
CV 72
6
18
47 (0x2F)
CV 73
7
22
56 (0x38)
CV 74
8
26
66 (0x42)
CV 75
9
30
75 (0x4B)
CV 76
10
33
85 (0x55)
CV 77
11
37
94 (0x5E)
CV 78
12
40
103 (0x67)
CV 79
13
44
113 (0x71)
CV 80
14
48
122 (0x7A)
CV 81
15
51
132 (0x84)
CV 82
16
55
141 (0x8D)
CV 83
17
59
151 (0x97)
CV 84
18
62
160 (0xA0)
CV 85
19
67
170 (0xAA)
CV 86
20
70
179 (0xB3)
CV 87
21
74
188 (0xBC)
CV 88
22
77
198 (0xC6)
CV 89
23
81
207 (0xCF)
CV 90
24
85
217 (0xD9)
CV 91
25
87
226 (0xE2)
CV 92
26
92
236 (0xEC)
CV 93
27
96
245 (0xF5)
CV 94
28
100
255 (0xFF)
Adjust the Forward and Reverse Trim
The DSD provides two CVs for adjusting or ‘trimming’ the forward and reverse speeds.
CV 66, Forward Trim
CV 95, Reverse Trim
These CVs multiply all data points in the speed tables by a factor of n/128 (n is the CV value) allowing the overall
speed curve to be adjusted up or down without reloading all 28 data points again.
These CVs may contain any value between 0 and 255 (0xFF). Trim values between 129 (0x81) and 255 (0xFF) will
increase speed curve values between 100% and 200% in 1% steps. Trim values between 1 and 127 (0x7F) will
decrease speed curve values between 1% and 99%. A value of 128 (0x80) yields a scaling factor of 1.0 and has no
effect on the speed curve.
Using different values for the forward and reverse trim will yield different forward and reverse speeds.
Adjust the Motor Drive Frequency
Virtually all DCC decoders, including the DSD, drive the locomotive motor using a technique called Pulse-Width-
Modulation or PWM. PWM works by alternately switching the motor from full off to full on. If the motor is switched fast
enough, the speed can be controlled by varying the ratio between the time the motor is on and the time the motor is
off. One drawback to PWM is that it can cause the locomotive to buzz, sometimes quite loudly, at low speeds.