Digitrax decoders allow for operation on both Digital Command Control (DCC) powered and on traditional Direct Current (DC) powered model railroads. Decoders from other manufacturers may or may not have this feature
Modern Digitrax Decoders are shipped with analog functions enabled to allow you to have working functions on locos on either type of layout without changing any CV values. (Series 3 decoders and later)
When a Digitrax Series decoder with analog functions enabled moves from a DCC track section to an analog track section, the functions that were active on DCC will remain active on DC. For these decoders, CV13 is not available because it is not needed.
Earlier Digitrax decoders require you to set the value of CV13 to 255 to enable analog functions
The analog functions enabled CV, CV13 lets you define which functions are active when the decoder is operating on DC track power. If you want function leads F0 forward and reverse and F1 through F6 to be active when on DC (for example when using a short DC track as "brake section") program CV13 for a CV value of 255 (xFF Hex). The factory default value for CV13 is 00, which turns OFF all functions when on DC track. Even though the motor will stop on DC power, the functions will still operate if CV13 is programmed for them to do so. To find the best settings for you experiment with the values until you get the desired settings.