Serge NOEL
196 lines
8.8 KiB
Plaintext
196 lines
8.8 KiB
Plaintext
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<title>JMRI: DecoderPro - Multi-Decoder Tool</title>
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<h1>JMRI: DecoderPro User Guide</h1>
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<h2>Multi-Decoder Tool</h2>
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Digitrax invented a <a href="#digitraxproposal">mechanism</a> for having more than one
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decoder in locomotive, and still be able to read and write them separately. It uses CV15 and
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CV16 in a particular way to do this.
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<p>CV16 is the ID of a particular decoder; if you have more than one decoder in a locomotive,
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they should have different values in CV16.</p>
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<p>CV15 is used to unlock one decoder (and lock the others), so it can be written.</p>
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<p>Only decoders that have the value in CV15 equal to the value in CV16 will respond to reads
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and writes. Since you're supposed to originally set up the two decoders with different CV16
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values, this means you can use CV15 to select which decoder you want to talk to.</p>
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<h2>DecoderPro's Handling of CV15 and CV16</h2>
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Really, the DecoderPro "paned programmer" shouldn't handle CV15 and CV16 at all. They're not
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really "configuration data", in the sense that you can freely adjust them and see what they
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do. Rather, CV16 is a "set once before assembling the locomotive", and CV15 is an operational
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command "which decoder can talk now".
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<p>If a DecoderPro user did a write-all-sheets and changed either of those, future
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programming operations would be problematic.</p>
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<p>Hence, people writing decoder definitions are strongly encouraged not to include CV15 and
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CV16 (when they are used for decoder lock) in their definitions, or to include them only as
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"constant" CVs so the program will not write them. The user can then program those CVs using
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the "Single CV Programmer".</p>
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<h2>The Multi-Decoder Tool</h2>
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<a href="images/MultiControl.gif"><img src="images/MultiControl.gif" width="121" height="283"
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class="floatRight" alt="multi decoder tool"></a> When this feature was first coming into use,
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a "Multi-Decoder Tool" was written for JMRI (see image to right).
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<p>It has several parts.</p>
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<p>At the top are 8 buttons that you can click to unlock a particular decoder in the
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locomotive. E.g. if you click "3", the decoder configured with "3" in CV16 will be unlocked.
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If possible, the program tries to verify that the decoder is present and communicating; the
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status is shown in the middle of the window ("OK" in the illustration).</p>
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<p>If you click the "Legacy" button, all decoders with the lock feature will be locked out.
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This is so you can write to an additional decoder without the lock feature. E.g. if you have
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one decoder with, say "2", and one without the lock feature, you can still configure them
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by:</p>
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<ol>
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<li>Click "2" - both decoders are now active.</li>
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<li>Write the information for "2", which will go to both.</li>
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<li>Click "Legacy", locking out "2".</li>
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<li>Write the information for the non-locking decoder, overwriting what you put in it
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above</li>
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</ol>
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Yes, that's ugly, but it can be made to work.
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<p>In the center are some buttons for automated operations you might find useful:</p>
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<ul>
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<li>"Search" - walks through a <u>long</u> series of writes and reads to determine which
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decoders are present. Buttons for decoders that aren't present will be disabled (grayed
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out).</li>
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<li>"Reset" - sometimes a decoder, even if installed by itself in the locomotive, can get
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accidentally locked when CV15 and/or CV16 is set to some spurious value. This button does a
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bunch of reads and writes to figure out what's happened and unlock the decoder.</li>
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<li>"Init DH163 + SoundTraxx" - If you have a DH163 or similar decoder with the lock
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feature, plus another decoder without the feature, this button works through a series of
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operations to configure the Digitrax lock feature so you can use it. (Normally you'd take
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the locomotive apart so as to be able to load the Digitrax CV16 value).</li>
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</ul>
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<p>Finally, the bottom part of the page allows you to control the programming mode in
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use.</p>
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<p>Although it's possible to use this tool in "Ops mode" (programming on the main), in that
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case it's not able to confirm operations, so one can't be 100% sure that the right decoder is
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selected.</p>
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<h2 id="digitraxproposal">Digitrax's Original Proposal</h2>
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<p>DCC users sometimes want to install more than one decoder in a single locomotive. One
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common case is using separate decoders for motor control and sound. Because these decoders
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often need to have their CVs configured separately, a mechanism is needed to communicate with
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only one at a time.</p>
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<p>This mechanism must be able to:</p>
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<ol>
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<li>Do service-mode read and write from a specific decoder, with no need to disconnect
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other decoders electrically.</li>
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<li>Discover the type of decoder(s) present inside a locomotive, without disassembly, and
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despite multiple decoders being present.</li>
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<li>Work with existing DCC systems without modification</li>
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</ol>
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<h3>Proposal:</h3>
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CV16 will carry a number from 0 to 7 inclusive. This is called the "ID number". This number
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identifies a single decoder, so a unique value must be assigned to each decoder in a
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particular locomotive. Because most users will use this mechanism with decoders that provide
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different functions, the recommended coding is:
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<pre>
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0: Reset value, as shipped
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1: Motor decoder
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2: Sound decoder
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3: Function-only decoder (e.g. for additional lights)
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</pre>CV15 is used to select the decoder that will respond. When the values in CV15 and CV16 are
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equal, all CVs in the decoder can be read or written. When the values in CV15 and CV16 are not
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equal, only CV15 can be written.
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<p>Some manufacturers may want to provide a bit in a CV to enable/disable this feature. If
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so, that should be in a CV reserved for the manufacturers use, as no NMRA CV has been
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reserved for this purpose.</p>
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<p>Note that a command to reset the decoder to default CV values must not be acted upon
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unless the CV15 and CV16 values are equal. This prevents the user from accidentally resetting
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multiple decoders at the same time, and losing the ability to separately address them.</p>
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<p>To configure decoders at installation:</p>
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<p>Before installing each decoder in the locomotive:</p>
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<ol>
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<li>Connect it to the programming track all by itself</li>
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<li>Write 8 to CV8 to ensure CV15 and CV16 are both zero</li>
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<li>If desired, read CV15 to confirm that the decoder can be addressed (This is a read of
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0, hence fast)</li>
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<li>Write CV16 to the desired ID number, e.g. 2</li>
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<li>Write CV15 to the ID number</li>
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<li>Configure the rest of the decoder</li>
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<li>Disconnect it and install it in the locomotive</li>
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</ol>
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Repeat in turn for each decoder to be installed
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<p>Note that if the user is installing only one decoder, there is no need to modify the
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default values of zero in CV15 and CV16.</p>
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<p>To access a decoder after installation:</p>
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<ol>
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<li>Write the ID of the desired decoder into CV15</li>
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<li>Read or write other CVs as needed</li>
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</ol>
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To identify the decoder(s) present in a locomotive:
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<ol>
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<li>Write a 0 to CV15</li>
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<li>Attempt to read a 0 from CV16.</li>
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<li>If no acknowledge is received, there is no decoder with ID 0. If an acknowledge is
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received, a decoder with ID 0 exists.</li>
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</ol>
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Repeat this process for ID 1 through 7 to check for those.
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<p>Because the ID values are low, a successful read is quite fast. An unsuccessful read, i.e.
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when the decoder is not present, will take some time on many existing command stations, but
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eventually give an answer. This can be made faster in the future by having command stations
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attempt to read just the expected value, instead of 0 to 255, in the absense of an
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acknowledge.</p>
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