Glossary of Terms#

Analog Front-end (AFE)#

This refers to processes and components from input of a channel through its signal processing FPGA.

Analog to Digital Converter (ADC)#

This chip samples the analog signal and digitizes it. The digitized signal is then sent to the FIPPI for processing. In some cases module’s serial number can be used to determine information about the ADC.

ADC Information based on Serial Number#

For modules with serial number greater than 1034, the ADC’s information is stored in the modules I2C serial EEPROM starting at address 99 and taking up 3 bytes.

Serial Number	Rev	ADC Bit Resolution	ADC Sampling Frequency (MSPS)
0 - 274	A - D	12	100
1000 - 1034	F	12	250

Bit Resolution#

This refers to the bit resolution of the module’s ADC. This value determines how precise the ADC can sample the incoming signal. It provides a limit on the system’s energy resolution. Typical bit resolutions are 12, 14, and 16.

Crate#

This refers to the chassis that holds the modules. The crate provides several critical functions:

it interfaces with the host computer via the crate controller,
it provides channels for the modules to communicate with each other,
and it delivers power to the modules.

The first slot in a crate is reserved for the crate controller. The remaining slots (2+) are available for Pixie-16 modules.

Revision	Crate Manufacturer	Connection Type	Available Slots
A	ELMA	PCI	8
B	ELMA	PCI	8
C	ELMA	PCI	14
D	Wiener	PCI	14
E	Wiener	PCIe	14

Crate Controller#

This is a National Instruments device that allows users to interact with the modules stored in a crate. It’s always installed in the first slot of a crate. There are various types of crate controllers. Some of these come with integrated computers making the crate a self-contained unit.

Digital Signal Processor (DSP)#

The device on the module that handles some calculations, run control, etc.

DSP Variables#

A variable is any value defined in the DSP VAR file. Variables can be used for both input and output. They are used at both the module and channel level. These values are not validated or transformed before being written to the DSP.

Examples include MultiplicityMaskL, LiveTimeA, ChanCSRa, CoincPattern, HardwareID.

Electrically erasable programmable read-only memory (EEPROM)#

An on-board chip that holds information such as the module’s Serial Number, Revision, and ADC information.

External FIFO (ExtFIFO) or List-Mode FIFO#

A chip on-board the module that handles information related to list-mode data runs. It’s accessible via the System FPGA.

Filter Integrator and Pulse Pileup Inspector (FIPPI)#

Refers to the pulse processing FPGA code, and sometimes it refers to an FPGA running the pulse processing code. See Signal-Processing FPGA for more information

Firmware#

The files that are loaded onto the module’s on-board DSP and FPGAs. Firmware varies depending on the module’s ADC’s bit resolution and sampling frequency. It’s critical that firmware matches with the module’s FPGAs. Firmware can be matched to the HW using the ADC information stored in the module’s EEPROM.

DSP#

The DSP firmware has 3 files: the image (.ldr), the listing (.lst), and the variable file (.var). The image file contains the actual code that we upload to the DSP while booting the module. The variable file contains a list of variables and their memory addresses. The listing file is primarily used for debugging purposes. It contains a full address list of the DSP’s memory, including internal variables.

For example, the Pixie16_revfgeneral_12b250m_firmware_release_05182019.zip release has the following files:

Pixie16DSP_revfgeneral_12b250m_r41847.ldr
Pixie16DSP_revfgeneral_12b250m_r41847.lst
Pixie16DSP_revfgeneral_12b250m_r41847.var

FPGA#

There are two types of FPGA firmware files: SYS and FIPPI. The SYS files get loaded onto the System FPGA. The FIP file gets loaded onto the FIPPI FPGA.

Host Bus Request (HBR)#

A procedure by which the System FPGA takes control of the bus connecting the FIPPI FPGAs from the DSP.

Load#

Software#

Refers to the act of moving data from the host system to the module. This includes putting the FIPPI firmware onto the chip or writing variables into the DSP memory.

Main Memory#

A chip on-board the module that houses spectra from histogram (MCA) runs.

Module / Board#

This refers to one unit of the Pixie-16 hardware that gets shipped to end users. Colloquially the boards are called by their alphabetical revision (A-H). A module is uniquely identified by its Serial Number.

Parameter#

Parameters are the user facing names of DSP Variables. These are used for inputting user values to the system. They are used at both the module and channel level. The value of the parameter undergoes validation and, in some cases transformation before being written to the hardware.

For example, users set the parameter VOFFSET in units of Volts. The SDK then transforms the value using the following transformation.

auto offset_dac = param::value_type (65536 * (value / DAC_VOLTAGE_RANGE + 0.5));

if (offset_dac > 65535)
    offset_dac = 65535;

The final value is then written to the DSP variable OffsetDAC.

Examples include TAU, XDT, MultiplicityMaskH, TRACE_DELAY.

Parameter Configuration#

Typically done by the user to setup the module for their specific requirements. Users often maintain their own configuration files in the form of bash scripts. These scripts make repeated calls to the parameter write API functions to configure the module.

A configuration file is specifically a file that deals with parameters.

PCI/PCIe Bridge#

A device installed in a host computer that allows a hard line connection to a crate controller. There are various types of bridges

PLX (Broadcom) Driver#

The driver installed on a host computer that facilitates communication between the host and the Pixie Module. Each Pixie-16 module contains a PLX 9054 chip. They show up under the host’s PCI bus as PLX 9054 devices. The latest PLX Driver can be downloaded directly from Broadcom.

0b:0c.0 Bridge: PLX Technology, Inc. PCI9054 32-bit 33MHz PCI <-> IOBus Bridge (rev 0b)

Broadcom acquired PLX Technologies and changed the name of the driver package.

Read#

Software#

Read refers to the act of moving data from the host system’s disk into host memory.

Revision#

Revision Refers to the Pixie-16 model number. Revisions are letter based starting with A and proceeding to F. This value is stored in the third byte of the module’s I2C serial EEPROM. For revisions B-F this value took the hex value associated with the revision (0xB - 0xF).

Sampling Frequency#

Refers to how quickly the ADC can sample the incoming signal. Typical sampling frequencies are 100, 250, and 500 Mega Samples per Second (MSPS). These values correspond to samples being taken every 10, 4, and 2 nanoseconds (ns), respectively.

Serial Number#

A number assigned to a module that uniquely identifies it within the company. Starting with Serial number 256 this value is stored in the first two bytes of the module’s I2C serial EEPROM. The serial number can be used to determine the module’s ADC sampling frequency and bit resolution in some cases.

Settings (Set) File#

Legacy Binary Settings file#

The Pixie-16 settings file (.set) contains the values of DSP parameters that are downloaded to the onboard DSP when a Pixie-16 is booted up. In addition, at the end of each run, either MCA run or list mode run, a settings file will be automatically generated together with either the MCA spectra file (.mca and .asc) or the list mode data file (.bin) and stored in either the MCA data folder or list mode data folder. Such a settings file also contains the run statistics data for the run that is just finished.

Each settings file contains settings for 24 Pixie-16 modules. And for each module, there are 1280 entries (32-bit for each entry). So the file size should be exactly 122,880 bytes. In the file, settings of module #0 are stored first, followed by module #1, #2, … and so on.

See Section 4.2.4 of the Pixie-16 User’s Manual for more information.

PixieSDK JSON Settings File#

We found that customers often want to view the contents of their binary settings files. They would often write software that allowed them to decode the file when coupled with a DSP VAR file. This causes issues since users may not recall which DSP VAR file produced the binary settings file. In addition, they may not have the information related to specifics of the FPGA firmware used.

To remove these issues, we now use a JSON settings file to setup and configure the DSP variables. This settings file is plain text, and contains a metadata field. This now provides users all of the information necessary to understand the contents.

We will no longer export an entire 2 crates worth of module configurations to this file. The SDK only exports configurations for active modules in the system. This file does not contain any of the read-only variables in the system. Users should access statistics data using the statistics functions.

Signal-Processing or FIPPI FPGA#

The on-board FPGA responsible for calculating filters trigger conditions and other information about the digitized signal.

System FPGA#

The System FPGA links the PCI slave with the DSP and the on-board memory, both the MCA memory and the list mode External FIFO memory. The host can read out the memory without interrupting the operation of the DSP. This allows updates of the MCA spectrum while a run is in progress and readout of list mode data from the External FIFO while the FPGA internal FIFO is being filled with events data.

The System FPGA also acts as an interface between the DSP, Signal Processing FPGAs and the backplane. It also has general purpose I/O connections available on the front panel. It can be configured to distribute trigger and hit pattern information from the Signal Processing FPGAs, and over the backplane to other Pixie-16 modules. In this way, coincidence or multiplicity decisions can be made to accept or not accept an event.

Variable#

A variable names a DSP memory address defined in the DSP’s VAR file. The variable addresses and names may change over time. It’s internal facing.

Examples include: ModCSRA, SlowLength, PreampTau

Variable Initialization#

The process by which the SDK reads a settings file into host memory, and then loads those variables into the module.