Mini-Acquisition Debugging and WFD Crate Check-out Procedures

This is the set of instructions for checking a crate of WFD cards after major work. For example, if it is necessary to replace a VME backplane, you will have to take the crate out and pull out all the WFD cards. Before starting new MACRO runs, you should check all the channels to make sure nothing got damaged.

In fact, be very careful when handling the WFD cards. The ASIC pins are very fragile. Watch out for dangling cable ends which can bend the pins. Also be careful with the power on: there was one instance of a cable dangling into the crate, shorting two pins together and burning them out.

There is other documentation for you to become familiar with the WFD system. For now, the principle documentation is online in the WFDINFO area. You can You can find this on the WWW at http://hep.bu.edu/~macro/wfd and on VAXGS in [MACROUSA.WFDINFO]. You might also find some past collaboration meeting talks to contain useful information.

Mini-Acquisition Sub-Menu

The tool for checking the crate out is the mini-acquisition. As of this writing, you must use a special version in [BOSTONPUB.KEARNS.COM]. Set default to that directory and execute @COMMAND. You will recognize most of the familiar options, plus a new one (26) labelled "new WFD CLI". CLI stands for Command Line Interface, and this is what you will use. When you enter this option you will be prompted for Workstation type. This is for HIGZ graphics display, just like PAW. Workstation type 121 works well with the Tektronix 4207 graphics terminals.

Next you will see a prompt, such as: [02000000]VMETEST>. You can type HELP to get a list of commands. For the purpose of this document, we will just discuss the commands necessary to check out the system.

The number inside the prompt is important. It is the hexadecimal crate base address from which channel base addresses are calculated from the channel number. Please refer to wfd-erp-map.txt in WFDINFO for channel to base address mapping. The leading digit is the supermodule number, so the base address for each crate is: $1000000, $2000000, $3000000, $4000000, $5000000, $6000000 for supermodules one through six. From this base, the program will calculate the correct VME address based on the requested channel number. To change this base address, you execute one of these commands:

VDREG_EX 1 2 1000000 (supermodule 1) VDREG_EX 1 3 2000000 (supermodule 2) VDREG_EX 1 2 3000000 (supermodule 3) VDREG_EX 1 3 4000000 (supermodule 4) VDREG_EX 1 2 5000000 (supermodule 5) VDREG_EX 1 3 6000000 (supermodule 6) For example, the first command specifies VMV branch 1, VME crate 2 and base address $1000000. On each uVaX, the VMV branch is always 1; VME crate 2 is assigned to SM-1, SM-3 and 5; VME crate 3 is assigned to SM-2, SM-4 and SM-6.

Dumping Data from a Channel

The most useful commands use channel number instead of a raw VME address. For this program, channel number runs from 0 to 39 for each supermodule except 0 to 43 for SM-1 and SM-6 because of the N/S face. To print out the data from a channel, use this command: WFDREAD 3 0 20 This reads from channel 3, starting at subaddress 0, 20 cycles of WFD data. A cycle of WFD data is defined as: one 16-bit timeword, four 4-bit discriminator words and four 8-bit ADC words (total of 8 bytes). There are two options for this command, S and >: WFDREAD 3 0 20 S starts readout at the STOP address WFDREAD 3 0 20 > FILE.TXT dumps the data to a file The WFDREAD command is useful as a quick test to make sure you are talking to the crate correctly, or to investigate the numeric data to look for unusual patterns such as a stuck bit.

Setting Discriminator Thresholds

To use the CLI to check out a crate of WFD cards, you will perform two operations: set the discriminator thresholds and use a graphical display to scan radioactivity data.

The threshold is set by the THRESH command, for example:

THRESH 3 2 5 In this command, you set channel 3, input 2 to a DAC value of 5. Each DAC bit is approximately -0.5 mV of threshold. So in this case, you have set the channel to our standard threshold of -2.5 mV (lower than our standard gain of -4 mV per photoelectron). Although you can set each input of each channel individually, the electronics is sufficiently stable to use the same threshold for all inputs of all channels. Therefore, we have two shortcuts in the code: THRESH 3 0 5 sets all 4 inputs of channel 3 to DAC=5 THRESH 0 0 5 b sets all 16 inputs of the board beginning with channel 0 The last command is what you will use to check out the crate. The first argument should be the first channel number in each of the 10 or 11 WFD boards per crate. So to get ready to scan the radioactivity in a crate, issue the following commands: THRESH 0 0 5 b THRESH 4 0 5 b THRESH 8 0 5 b THRESH 12 0 5 b THRESH 16 0 5 b THRESH 20 0 5 b THRESH 24 0 5 b THRESH 28 0 5 b THRESH 32 0 5 b THRESH 36 0 5 b THRESH 40 0 5 b <- only if North or South face present in this crate

Plotting a Waveform

Now, the WFD cards are configured with a low threshold and zero suppression turned on. (Notice how the program reports the default control register = $11? That indicates that zero suppression and rollover word is set on). See the control register documentation in WFDINFO.

Now you have to load data into the channels. With the PMT signals cabled up, simply push the START button on the WFD fanout, followed by the STOP button. The WFD's must be STOPPED to read data (the top LED is red).

To scan the radioactivity, make a graphic plot of signal voltage versus time using the ADCPLOT command. This command has a lot of options. For this test, the best command is:

ADCPLOT 3 0 4000 v This command reads data from channel 3, starting at subaddress 0 and displays 4000 usec of WFD cycles in Volts. The display has three separate graphs: voltage versus time, discriminator bits versus time and timeword versus time. The time axis (labelled in usec) is not real-time. It is a psuedo-time formed by stacking all of the zero-suppressed pulses up in sequence. You can keep track of real-time by looking at the timeword plot: it swings from top to bottom in 327 usec). Although the psuedo-time display is not so useful for data analysis, it is good for debugging since it shows you structure of the pulses that would otherwise be lost in a long time window.

In this display you will quickly see if there is some major defect in the data, such as: zero suppression is off, a discriminator bit is stuck on, a channel is missing or a channel is hot. This is what you are checking for. Before you get worried about a problem (such as zero-suppression), make sure you have performed all the initial steps correctly. Before you worry about input 4 missing data, make sure the channel is not one of the vertical face channels with only 3 inputs. A healthy channel will have approximately equal rate of pulses in all four inputs, and the individual pulses will look like radioactivity waveforms: narrow pulses a few tens of mV high.

You can zoom in on a window of the data by specifying a later starting time and a smaller window length. For example, this will display channel 3 from t=-900 usec for a length of 100 usec (in pseudo-time units):

WFDREAD 3 900 100 V If you leave off the V option, the plot will be in ADC counts. It may look strange because of the non-linear response of the frontend amplifier. The last part of the command is a character option which you can use to control the appearance of the plot. You may append characters in any order. Here is a list of other options: G draw a grid HG draw a fine grid (useful for calibrations) S begin data at the Stop address M draw Markers (warning: slow if there are lots of data points) W draw Waveform plot only D draw waveform and Discriminator plot only T add a title (specify the title last, no spaces (sorry) There is a command to make a hardcopy of what you see on the screen: HARDCOPY file.ps Be sure to delete old files after printing!

Summary

That completes this lesson on checking out a WFD crate. To quickly summarize the key steps:
  1. start mini-ACQ by @[BOSTONPUB.KEARNS.COM]COMMAND
  2. option 26... WFD CLI
  3. VDREG_EX 1 2-or-3 (SM)000000
  4. make sure WFD's are stopped
  5. THRESH 0 0 5 b ... do all 10 or 11 boards
  6. start and stop the WFDs using the WFD fanout
  7. ADCPLOT 0 0 4000 V ... do all 40 or 44 channels