DSC Problem Solving

The DSC system is not easy to handle. Many occuring problems cannot be solved easily. Here I try to give a little guide to solve DSC problems. In addition the content in this file may answer some FAQs about the DSC handling.

The Domino Sampling Chip setup is a very fragile system. It might be e.g. that there are very many address error messages about bad DSC addresses after working on the ADCs. A 'wrong' touch to the input cables to the DSC motherboards can be enough to screw up the whole system.
In most cases it might be enough to take new address values, because the touch of a cable may affect a small shift of the DSC baseline which shifts all address values.

How to sample new address data

Start odbedit on pc2106 from the directory online. Change directory by

cd Equipment/Trigger/Settings/DSC

A typical odb-file from this directory is dsc_setup.odb. You can see the possible values. Usually the Address Lock is set to boolian y. This means that the address values are kept untouched. The Auto lock counter variable defines after how many events the Address get locked. So first of all one has to set all addresses to '0' by

set "Address Min[*]" 0

set "Address Max[*]" 0

In adition one has to switch the Address lock to n and set a value for the Auto lock counter e.g. to 100:

set "Address lock" n

set "Auto lock counter" 100

After you have started a run for every RANDOM Trigger event, where all DSC channels fire, the address values are taken and after 100 of these events the minimum value and the maximum values are stored in the odb and the Address Lock will be set to boolian y. If one sees that there is only a change necessary for an individual channel one can set the min or max value by hand with the same command and the proper value instead of the '0', e.g.

set "Address Min[48]" 3030

Error messages from the DSC e.g. about bad address values are written into an individual log-file dsc.log. Here one can lookup if an DSC Alarm has occured.

In The DSC Address EXCEL sheet one can see the data taken from one odb-file after taking address data, taken into excel for graphical visualisation and calculating e.g. address distances.

The DSC Test program

The DSC Test program is used to setup the DSC system (adjust addresses and Zero suppression threshold voltages) as well as searching DSC problems.

The most important tool to debug and setup the DSC system is the standalone program DSC Test running on the Frontend PC. Before you start the program make sure, that the Frontend is not running. Start the b>DSC Test program by double clicking the Icon with an IC and the name b>DSC Test on the desktop. It opens DOS window and a menu shows up. The first two modes are only for very special debugging purposes. In mode 3 all chips are read out. This mode one should only use if the Zero Suppression is switched off (all chips are firing!). This can be selected by a jumper on the Controller. This mode can be used e.g. to set the address values by the potentiometers on the carriers.
In Mode 4 an address to channel relation will be calculated by a function. This mode is usable if e.g. a single channel is missing and Mode 5 is not usable therefore. In Mode 5 the program waits for a testpulse where all channels fire. Then it accumulates the address to channel data (actual value, min. max.; data get always updated). This mode is important to see if the system is working and to set the correct Zero Supression thresholds. After starting the program with a normal production or Cosmic trigger with Random events the address values should be collected within a few seconds. Then one can see that the address values in the upper block are always firing for different channels. The upper and lower bounds for the addresses can be seen in the next two blocks. One can check if the addresses are correct and that they are not overlapping.

One indication that something is running bad with the DSC system are the LEDs on the trigger and clock inputs of the FADC in the VME crate. In the past I have seen, that the clock LED is still on while the Trigger LED goes on and off. Whenever they are running asynchronous it is an indication for a more complicated problem. First of all one has to find out which motherboard induces the problem. This can easiest be done by unplugging them on the backside bus one by one and look after the standalone program ist started, if the Clock and FADC Trigger LEDs blink synchronous. It might be that it works again after unplugging the bus cable on the backside and replugging it. Sometimes you have to do it a few times (unplugging and replugging), but often this helps.

It might be that a DSC goes bust. The easy way is, if you are not able to fix a problem by the unplugging and replugging, then you should maybe replace carrier by carrier on the bad DSC motherboard, plug it back to the system and look how it behaves in the DSC Test Program. If this also doesn't help, exchange the motherboard. The bad motherboard also as the bad carrier has to be investigated for repair. The carrier can be tested by the test setup in the lab. A bad motherboard can be brought to Peter Dick from the Electronics Pool. If a DSC on a carrier has be exchanged, Silvan Streuli from the Horisberger Group can take a bad DSC off by a dentists drill. Then you have to glue a new DSC onto the carrier board.

Bring on a new DSC

For glueing a DSC onto a carrier use ARALDIT Rapid and mix it 1:1 with Alcohol. Use the pike of a needle to get a very small drop and put it onto the carrier. Put the DSC onto the drop of glue by a tweezers. You can press it slightly and correct its orientation by the use of a plastic tweezers. For bonding and coating you have to ask Silvan Streuli.

There are 7 complete spare carriers (they are all tested!). and in addition 7 DSC chips from the same series and in addition about 1000 DSC from another series. These chips are all on blocks of 6 DSC together with 2 cips from another experiment. They have to be cutted and tested, as descibed on the DSC Test Page.

The main part of the DSC Sequencer is an Altera epm7032s FPGA which produces all control signals from the input signals. The Controller and the necessary signals are described on theController Page Details on the necessary control sequences you can find on the DSC Homepage.

Details on the Motherboard

Description on the DSC 48 Motherboard

Learn how it looks like and what the components are for.

Layout of the multilayer motherboard and DSC carrier.

Pictures and PS-Downloads

Return to the DSC Main Page


H.P. Wirtz, last update 09-Aug-2000