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XIA microDXP Technical Reference Manual

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Technical Reference Manual
Information furnished by XIA LLC is believed to be accurate and reliable. However, no responsibility is assumed by
XIA for its use, or for any infringements of patents or other rights of third parties which may result from its use. No
license is granted by implication or otherwise under any patent or patent rights of XIA. XIA reserves the right to
change hardware or software specifications at any time without notice.
microDXP
Version 3.15
October 7, 2019
microDXP Hardware Revision: H (8)
ProSpect Software
Software Revision: 1.0.24
XIA LLC
31057 Genstar Rd
Hayward, CA 94544 USA
Email: support@xia.com
Tel: (510) 401-5760; Fax: (510) 401-5761
http://www.xia.com/

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  • Page 1 Information furnished by XIA LLC is believed to be accurate and reliable. However, no responsibility is assumed by XIA for its use, or for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of XIA.

  • Page 2: Table Of Contents

    Technical Reference Manual Version 3.15 Table of Contents Safety .............................. 7 Specific Precautions ..........................7 Power Source ............................7 Detector and Preamplifier Damage ....................... 7 Servicing and Cleaning ......................... 7 Warranty Statement ........................8 Contact Information: ..........................8 Manual Conventions ........................9 Introduction .........................
  • Page 3 1.7.4.1 Submitting a problem report: ..................20 1.7.5 Feedback ..........................21 1.7.5.1 Export File Formats ......................21 Using the microDXP ......................22 Hardware Settings ........................22 2.1.1 Preamplifier Type Selection ....................22 2.1.2 Input Signal Attenuation ..................... 22 Board State and Configuration ....................23 2.2.1...
  • Page 4 2.8.1.4 Pre-Trigger Position (TRACEPRETRIG)............... 34 2.8.2 Baseline Histogram ......................35 2.8.3 DSP Parameters........................35 MicroDXP Functional Description ..................36 Organizational Overview ......................36 The Analog Signal Conditioner (ASC) ..................36 3.2.1 Dynamic Range Reduction ....................37 3.2.1.1 Reset-Type Preamplifiers ....................37 3.2.1.2...
  • Page 5 Technical Reference Manual Version 3.15 3.2.2 Analog Gain ........................39 3.2.2.1 Nominal Gain ........................40 3.2.2.2 Switched Gain ......................... 40 3.2.3 Nyquist Criterion......................... 41 The Analog to Digital Converter (ADC) ..................41 The Filter, Pulse Detector, & Pile-up Inspector (FiPPI) ............. 41 3.4.1...
  • Page 6 Input Count Rate (ICR) and Output Count Rate (OCR) ............. 61 Throughput ..........................61 Appendices ........................... 63 Appendix A. MicroDXP Hardware Specification .................. 63 A.1 Board Dimensions and Mounting ....................63 A.2 Preamplifier Type Selector Switch ....................63 A.3 Input Signal Attenuation ......................63 A.4 Connector Locations and Pinouts ....................

  • Page 7: Safety

    Detector and Preamplifier Damage Because the microDXP does not provide power for the detector or preamplifier there is little risk of damage to either resulting from the microDXP itself. Nonetheless, please review all instructions and safety precautions provided with these components before powering a connected system.

  • Page 8: Warranty Statement

    In order to obtain service under this warranty, Customer must notify XIA LLC of the defect before the expiration of the warranty period and make suitable arrangements for the performance of the service.

  • Page 9: Manual Conventions

    Technical Reference Manual Version 3.15 Manual Conventions The following conventions are used throughout this manual Convention Description Example » The » symbol leads you The sequence through nested menu items File»Page Setup»Options directs you to pull and dialog box options.

  • Page 10: Introduction

    This version of the manual describes the new ‘blue’ microDXP pictured on the right below. If your microDXP is green, as pictured on the left, please refer to the older version 1.0.2 of this manual. Figure 1-1: The new microDXP pictured on the right was released in 2015.

  • Page 11: Embedded Systems Features

    1.2 Hardware Requirements 1.2.1 Host Computer The microDXP can communicate with any host computer/controller via RS-232. Windows 7 or later is required to operate via USB. 1.2.2 Detector/Preamplifier The microDXP accommodates nearly all detector preamplifier signals. The two primary capacitor-discharge topologies, pulsed-reset and resistive-feedback, are supported.

  • Page 12: Power Requirements

    The microDXP board is RoHS compliant. 1.3 Hardware Options The microDXP hardware is both powerful and flexible. XIA is pleased to offer a number of assembly options that will produce the best value for a given set of requirements. The specification sheet provided with your microDXP lists the options that have been implemented.

  • Page 13: Analog Input

    +/-5.50 V is required, and the ripple requirement can be relaxed a bit. If planning to use the MicroComU companion board, choose the variant of the microDXP that includes on-board voltage regulators. Aside from this, the MicroComU board will take care of generating all required voltages for the microDXP, at the specified currents and noise performance.

  • Page 14: Pipeline Clock Speed Choice

    25.5 dB of digitally-controlled analog gain in 16 discrete steps in addition to the digital fine gain trim. This allows the microDXP to be optimized for a wide range of x-ray energies and a wide variety of detectors. The microDXP can be further optimized via a custom input-attenuation circuit, which also allows for customization of the input impedance.

  • Page 15: Custom Firmware

    The MicroComU board acts as both a carrier and companion board for the microDXP. Power for the MicroComU/microDXP board set is provided via the AC wall adapter provided with the USB Rapid Development Kit.

  • Page 16: Example 2. General-Purpose Spectrometer Using Rs232 And Custom Breakout Board

    2. Power supplies for the microDXP must be provided. Optional voltage regulators for the analog circuitry are included on the microDXP for systems in which high- quality power supplies are not available.
  • Page 17 (e.g. RS-232) is also included so that ratios corresponding to new alloys can be defined, and new firmware uploaded without dismantling the hardware; or, alternatively, the microDXP could periodically be run in full MCA mode under computer control for diagnostic purposes.

  • Page 18: Software Overview

    Figure 1-4: A system with a fully embedded host and user interface, with real time controls via the Auxiliary digital I/O. Although the figure above shows a flex cable used to interface the microDXP board to the Advanced Interface board, it is also possible to use the board-to-board connector on the microDXP, as was done with the recently introduced MicroComU companion board.

  • Page 19: Firmware

    1.7 Support A unique benefit of dealing with a small company like XIA is that the same people who designed them often provide the technical support for our sophisticated instruments. Our customers are thus able to get an in-depth technical advice on how to fully utilize our products within the context of their particular applications.

  • Page 20: Email And Phone Support

    1.7.4 Email and Phone Support The microDXP comes with one year of email and phone support. Support can be renewed for a nominal fee. Please call XIA if your support agreement has expired. The XIA Digital Processors (DGF & DXP) are digitally controlled, high performance products for X-ray and gamma-ray spectroscopy.

  • Page 21: Feedback

    For general questions and DXP hardware issues please email support@xia.com 1.7.5 Feedback XIA strives to keep up with the needs of our users. Please send us your feedback regarding the functionality and usability of the microDXP and ProSpect software. In particular, we are considering the following development issues: 1.7.5.1...

  • Page 22: Using The Microdxp

    2 Using the microDXP This chapter provides a general outline of microDXP operations. XIA recommends using the ProSpect software as a microDXP configuration platform in all phases of production. For a step-by-step ‘Getting Started’ guide using ProSpect, including hardware setup instructions, please refer to the Rapid Development Kit User Manual.

  • Page 23: Board State And Configuration

    Contact XIA for assistance. 2.2 Board State and Configuration The microDXP boots itself upon power up, and is shortly thereafter ready to acquire data with the same set of operating parameters used in the previous run. The first time the microDXP is powered on, detector and preamplifier related parameters will be in the factory default state.

  • Page 24: Serial Number

    The microDXP must have DSP and FPGA code pre-loaded in non-volatile memory that is appropriate for the preamplifier type used, and the microDXP hardware must be set type via a miniature DIP switch (refer to Appendix A for the switch location and settings).

  • Page 25: Decay Time: Taurc

    The advanced processor settings enable and disable various Digital X-ray Processor functions, and correspond to bits of the DSP parameter RUNTASKS. Typically these settings should only be modified as directed by XIA support staff. In ProSpect, the advanced processor settings are accessed in the Advanced tab of the Settings panel.

  • Page 26: Mca Settings And Gensets

    RS-232 Command Specification for details. 2.4.2 MCA Size and Bin Width The microDXP MCA format is quite flexible, with adjustable Number MCA Bins ranging up to 8192, and adjustable granularity via the MCA Bin Width setting. The DSP doesn’t constrain the relationship between these settings, so it’s possible to define a spectrum that exceeds the practical limits of the ADC, which should be avoided.

  • Page 27: Base Gain, Switched Gain And Digital Base Gain

    Technical Reference Manual Version 3.15 MCA Bin Width = BINMULTIPLE = 2 BINGRANULAR Equation 2-2 For simplicity, we recommend setting the BINGRANULAR = 4, such that the MCA Bin Width is set directly via BINMULTIPLE. Note that changing BINMULTIPLE (either directly or via BINGRANULAR) does affect the Digital Gain, per Equation 3-8.

  • Page 28: Reading The Current Genset

    Technical Reference Manual Version 3.15 2-5 above, and then set the Digital Base Gain to compensate for the difference, as described in §3.4.3. Use command 0x8F to save the current GENSET. Please refer to the RS-232 Command Specification for details.

  • Page 29: Baseline Average Length

    Technical Reference Manual Version 3.15 parameters THRESHOLD, BASETHRESH and SLOWTHRESH correspond to thresholds applied to the Trigger (fast), Baseline (intermediate), and Energy (slow) filters, respectively. Please refer to section for a thorough discussion of thresholds. Each PARSET includes 5 different settings for THRESHOLD, BASETHRESH and SLOWTHRESH, corresponding to the 5 MCA formats, or GENSETs.

  • Page 30: Advanced Filter Settings

    2.6.2 Download a Master Parameter Set… In ProSpect select Download… from the Firmware menu to write the parameters in the XUP file you created to a second microDXP. Browse to the desired XUP file and location and press [Download]. 2.7 Data Acquisition This section describes the most common data acquisition procedures.

  • Page 31: Starting A Run

    By default (i.e. PRESET = 0) a run in progress continues until a ‘stop run’ command is issued. The microDXP can be configured to automatically terminate until a preset time or number of input or output counts has elapsed, as described below in §2.6.5. In such cases the ‘stop run’...

  • Page 32: Specifying Fixed Run Lengths

    Command Specification for details. 2.7.5 Specifying fixed run lengths By default, the microDXP acquires data until a stop command is received from the host. Alternatively the microDXP can automatically terminate data acquisition runs based upon the real time, live time or the number of input or output counts exceeding a preset value.

  • Page 33: Trace Type (Tracetype)

    Technical Reference Manual Version 3.15 The RS-232 command to read the diagnostic trace is 0x11. Please refer to the RS-232 Command Specification for details. 2.8.1.1 Trace Type (TRACETYPE) Trace Type (TRACETYPE) selects the vector that is acquired. Note: all of the Trace Type signals except for ADC and ADC Average are signed 2’s complement vectors that have been sign-extended or attenuated to 16-bit magnitude, and the sign-bit has been inverted such that 0 is shifted to 32,768.

  • Page 34: Trigger Type (Tracetrig)

    Technical Reference Manual Version 3.15 50 ns 25 ns 65535 (max) 1.6384 ms 819.2 ms Table 2-5: Sampling Interval as a function of TRACEWAIT and ADC sampling rate 2.8.1.3 Trigger Type (TRACETRIG) The trace can be triggered or un-triggered, depending on the Trigger Type (TRACETRIG), which does not affect triggering for the MCA acquisition, i.e.

  • Page 35: Baseline Histogram

    Technical Reference Manual Version 3.15 0.4% 4096 255 (max) 8000 100% Table 2-7: Pre-Trigger Position 2.8.2 Baseline Histogram A histogram of instantaneous baseline samples is also available. Refer to §4.4 for a discussion of baseline acquisition and averaging. In ProSpect, select the Baseline tab in the Main panel. Press the [Get Baseline] button to display the baseline histogram.

  • Page 36: Microdxp Functional Description

    Technical Reference Manual Version 3.15 3 MicroDXP Functional Description 3.1 Organizational Overview The DXP channel architecture is shown in Figure 3-1. The four major operating blocks are the Analog Signal Conditioner (ASC), digital Filter, Peak detector, and Pileup Inspector (FiPPI), Digital Signal Processor (DSP), and PIC microcontroller.

  • Page 37: Dynamic Range Reduction

    Reset-Type Preamplifiers For reset-type preamplifiers the dynamic range reduction is accomplished using a novel technology, for which XIA has received US and international patents, and which is indicated in Figure 3-2. Here a preamplifier output is shown which cycles between roughly -3.0 Vand -0.25 V.

  • Page 38: Rc-Feedback Preamplifiers

    Technical Reference Manual Version 3.15 Figure 3-2: A saw tooth function having the same average slope as the preamp output, which ranges from -3.0 V to -0.25 V, is subtracted from it and the difference amplified and offset to match the 2.0 V input range of the ADC.

  • Page 39: Analog Gain

    The single ‘base gain knob’ was easy to use, but we’ve found that VGA devices introduce excessive noise, temperature drift, and significant non-linearities into the signal. In a significant departure from the previous design, the updated (blue) microDXP design now employs a digitally-controlled switched-gain amplifier architecture with 16 coarse analog gain settings for dynamic ranging in concert with finely adjustable digital gain for energy calibration.

  • Page 40: Nominal Gain

    DSP parameters NOMGAIN (UQ1.15 format unsigned mantissa) and NOMGAINE (exponent). It is determined by the fixed amplification stages in the microDXP analog front-end circuit and by the Input Attenuation setting (see §2.1.2). Nominal Gain = 0.825 * Input Attenuation...

  • Page 41: Nyquist Criterion

    Technical Reference Manual Version 3.15 23.58 15.11 15.11 25.23 18.25 18.25 26.91 22.15 22.15 28.66 27.09 27.09 30.32 32.79 32.79 32.16 40.55 40.55 33.84 49.20 49.20 35.59 60.19 60.19 37.25 72.85 72.85 * Base Gain values shown assume that the Digital Base Gain = 1.000 Table 3-2: Relationship between SWGAIN and Switched Gain.

  • Page 42: Fippi Variants

    S1 must be set according to the code variant, as described in Appendix A. Additionally, any use of the auxiliary digital I/O will require per-instance FiPPI configuration variant. Please contact XIA to discuss the use of the auxiliary digital I/O. FiPPI...

  • Page 43: Mca Bin Width

    Technical Reference Manual Version 3.15 +/- 22%. It is stored in a new pair of GENSET parameters DGAINBASE (UQ1.15 format unsigned mantissa) and DGAINBASEEXP (2’s-complement signed exponent), DGAINBASE DGAINBASEEXP Digital Base Gain = 32768 Equation 3-9 For best results DGAINBASE should be constrained between 32768 and 65535, and DGAINBASEEXP between -2 and 1.

  • Page 44: Parallel Flash Eeprom

    Version 3.15 3.5.1 Parallel Flash EEPROM The microDXP also includes on-board non-volatile memory, which allows for the storage and retrieval of firmware and settings. A parallel flash EEPROM, accessed by the DSP, is used to store FiPPI configuration codes and parameter sets, i.e. the GLOBSET, GENSETS and PARSETS.

  • Page 45: Rs-232 Serial Port

    Two I2C devices are included on the microDXP itself (described below), and the bus is wired to both interface connectors to provide for microDXP control over, or monitoring of, other devices.

  • Page 46: Board-To-Board Interface

    Flex Cable Interface Resources 3.7.3 Board-to-Board Interface A high-density board-to-board connection is also included on the microDXP. The so-called high-speed interface includes all resources carried on the flex-cable interface, plus Direct Memory Access (DMA) to the DSP. It was included for applications requiring very fast data transfer rates.

  • Page 47: Digital Filtering: Theory Of Operation And Implementation Methods

    Implementation Methods This chapter provides an in-depth discussion of x-ray pulse-processing theory both generally and as implemented in the microDXP. The topics include how digital filters work, x-ray detection, thresholds, baselines, pileup inspection, and input and output count rates. Topics are covered to illustrate the theoretical issues, practical implementation, and how to adjust parameters to obtain best performance.
  • Page 48 Figure 4-2: The large-signal reset waveform for a reset-type preamplifier with positive signal polarity, as displayed on a real oscilloscope. Note that the large signal character is not displayed in the microDXP diagnostic trace readout, e.g. used in ProSpect’s Scope diagnostic tool, looks quite different because of the dynamic range reduction carried out in the ASC, as described in §3.2.1.

  • Page 49: Rc-Type Preamplifiers

    Technical Reference Manual Version 3.15 4.1.2 RC-Type Preamplifiers Figure 4-3a is a simplified schematic of an RC-type preamplifier, wherein C is discharged continuously through feedback resistor R . The output of an RC-type preamplifier following the absorption of an x-ray of energy Ex in detector D is, again, a voltage step of amplitude V .
  • Page 50 Technical Reference Manual Version 3.15 as shown in Figure 4-4, averages are computed over the two regions marked “Length” (the “Gap” region is omitted because the signal is changing rapidly here), and their difference taken as a measure of V .

  • Page 51: Trapezoidal Filtering In The Dxp

    1 Mcps, but it costs over $15K per channel. The DXP processing system developed by XIA takes a different approach because it was optimized for very high-speed operation and low cost per channel. It implements a fixed...
  • Page 52 Technical Reference Manual Version 3.15 order measure of the filter’s noise reduction properties, is thus 2L+G. This raises several important points in comparing the noise performance of the DXP to analog filtering amplifiers. First, semi-Gaussian filters are usually specified by a shaping time. Their peaking time is typically twice this and their pulses are not symmetric so that the base width is about 5.6 times the shaping time or 2.8 times their peaking time.

  • Page 53: Baseline Issues

    Technical Reference Manual Version 3.15 4.4 Baseline Issues 4.4.1 The Need for Baseline Averaging Figure 4-6 shows the same event as is Figure 4-5 but over a longer time interval to show how the filter treats the preamplifier noise in regions when no x-ray pulses are present. As may be seen, the effect of the filter is both to reduce the amplitude of the fluctuations and reduce their high frequency content.

  • Page 54: Raw Baseline Measurement

    Technical Reference Manual Version 3.15 amplifier’s noise contribution should be essentially negligible, though achieving this in the mixed analog-digital environment of a digital pulse processor is a non-trivial task. In the general case, the mean baseline value is not zero. This situation arises whenever the slope of the preamplifier signal is not zero between x-ray pulses.

  • Page 55: X-Ray Detection & Setting Thresholds

    This is the primary cause of degraded energy resolution at high rates. The microDXP now employs a proprietary circuit that virtually eliminates this problem, resulting in industry-leading count rate stability.

  • Page 56: Peak Capture Methods

    This is a significant source of the enhanced throughput found in digital systems. Once an active threshold is exceeded, the microDXP employs one of two methods to capture the slow energy filter output such that the best measure of V results: 1.

  • Page 57: Peak Sampling Vs. Peak Sensing

    Technical Reference Manual Version 3.15 4.6.2 Peak Sampling vs. Peak Sensing The figures below demonstrate the two approaches. In Peak Sensing mode the slow filter output is monitored over a finite interval of time, and the maximum value within that interval is selected.

  • Page 58: Pile-Up Inspection

    Technical Reference Manual Version 3.15 Figure 4-8: In Peak Sampling mode the slow filter output is sampled a fixed time after the x-ray is detected. PEAKSAM must be set properly to achieve optimum performance. In our experience values at the low end (i.e. PEAKSAM ~ SLOWLEN) tend to work better.

  • Page 59: Slow Pileup

    Technical Reference Manual Version 3.15 4.7.1 Slow Pileup The first kind of pileup is slow pileup, which refers to pileup in the slow channel. This occurs when the rising (or falling) edge of one pulse lies under the peak (specifically the sampling point) of its neighbor.

  • Page 60: Fast Pileup

    Technical Reference Manual Version 3.15 Figure 4-9: A sequence of 5 x-ray pulses separated by various intervals to show the origin of both slow channel and fast channel pileup and demonstrate how the two cases are detected by the DXP.

  • Page 61: Input Count Rate (Icr) And Output Count Rate (Ocr)

    Technical Reference Manual Version 3.15 will never exceed some maximum width, defined by MAXWIDTH. Thus, if the width of the fast filter output pulses is measured at threshold and found to exceed MAXWIDTH, then fast channel pileup must have occurred. This is shown graphically in Figure 4-9, where pulse 3 passes the MAXWIDTH test while the piled-up pair of pulses 4 and 5 fail the MAXWIDTH test.
  • Page 62 Technical Reference Manual Version 3.15 OCR = ICR e (-ICR τ Equation 4-14 Where  is the dead time per event, given approximately by Equation 4-15. In practice, the dead time per event will be slightly higher due to preamplifier resets and ASC tracking steps, both of which incur additional dead time.

  • Page 63: Appendices

    Select RC for RC-feedback preamplifiers. Note that the setting must match both your detector preamplifier and the firmware that is installed in non-volatile memory, as indicated in the Preamplifier Type field in the Detector tab. Please contact XIA if you have the wrong type of firmware installed.
  • Page 64 IDMA access to DSP memory for transfer rates up to 10 Mbytes/sec. This parallel IDMA interface is used as the basis for the microCOMU USB interface. The latest microDXP hardware includes an on-board mini-USB 2.0 interface (J8), simplifying the implementation design process for embedded systems. The customer need only provide power and auxiliary digital I/O connections via the flat-flex cable or board- to-board connector.
  • Page 65 Technical Reference Manual Version 3.15 Hirose P/N: DF13-2P-1.25H (mating P/N: DF13-2S-1.25C; crimp contact P/N: DF13-2630SCFR) Pin # Name Description SIGNAL Preamplifier output signal Internal ground connection Table A-2: Pin assignments for the 2-conductor SMT header analog input connection. J4 - Analog Input: thru-hole coaxial (TOP SIDE) LEMO P/N: EPK.00.250.NTN...
  • Page 66 Technical Reference Manual Version 3.15 ProgClk PIC programming clock Aux0 Auxiliary configurable digital I/O line: connects to FiPPI Aux1 Auxiliary configurable digital I/O line: connects to FiPPI Internal ground connection Aux2 Auxiliary configurable digital I/O line: connects to FiPPI...
  • Page 67 Internal ground connection EWR* IDMA write strobe (Active LO) ESel* IDMA device select INPUT (must be asserted LO to communicate with the microDXP) ERdy* IDMA data ready (Active LO) OUTPUT ERD* IDMA read strobe (Active LO) Even-numbered pins (top to bottom along the left-side of the connector as shown...

  • Page 68: Power Supplies

    If a switching supply is used, it should be well shielded from the microDXP. By default, supply voltages of +/-5.5V are regulated on-board by default to generate +/- 5.0V to power the analog components.

  • Page 69: Appendix C. Genset Specification

    Technical Reference Manual Version 3.15 PRESETLENLO Low word of preset run length PRESETLENHI High word of preset run length PRESET Preset type (0: no preset, 1: real time, 2: live time, 3: output events, 4: input events) RESETINT Reset time in microseconds...

  • Page 70: Appendix D. Parset Specification

    Technical Reference Manual Version 3.15 SCATIMEON Assertion time (in clock periods) of the SCA real- time digital outputs SCATIMEOFF Minimum off time (in clock periods) of the SCA real-time digital outputs SCA0LIMLO Lower limit for SCA0 SCA0LIMHI Upper limit for SCA0...

  • Page 71: Appendix E. Rs-232 Communications

    SLOWTHESH0-4 Per-GENSET slow filter threshold values. Appendix E. RS-232 Communications This appendix describes the basic microDXP RS-232 command and response protocol. Please refer to the RS-232 Command Specification (a separate document) for a detailed presentation of all RS-232 commands. The general structure for commands and responses is as follows: [Esc][Command][Ndata (2 bytes)][data1]…[dataN][xor CS]...
  • Page 72 Technical Reference Manual Version 3.15 0x00 (status is ok) 0x0B (the low byte of the new RUNID=0x1B=27) 0x10 (the high byte of the new RUNID=0x1B=27) 0x18 (bitwise XOR—excludes escape character) Response (if unsuccessful): 0x1B (the escape character) 0x00 (the command is always returned)

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