Hardware Protocol

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The DRV-2000 is the hardware interface between your SEM and PC.  It was designed specifically for high resolution, low noise digitization of SEM images.  The DRV-2000 employs the most appropriate technologies to facilitate this goal.

  The DRV-2000 SEM-PC interface.

The DRV-2000 interface can drive ANY SEM directly, except for one.  The JEOL model 35 requires non standard deflection inputs.  If you have a JEOL 35,   We manufacture an external 'black box' to accommodate the JEOL 35's unique requirements.

General description:

Signal digitization: The SEM-PC interface allows both analog and digital signals to be quantified. Analog inputs for SE and BSE signal digitization are totally independent, and consist of programmable video prescaling circuitry, signal integrators, and 12 bit instrumentation quality Analog to Digital converters. Digital inputs are provided for quantifying events such as Xray signals. Typically, systems are capable of quantifying up to 4 channels with a maximum count limit of 65,536 (2^^16).

Scan Control: The SEM-PC interface is capable of controlling the beam position of the SEM to 1 part in 65384. X and Y scans are addressable via independent high quality Digital to Analog converters (DACs). 

Miscellaneous: The SEM-PC interface also contains programmable timing circuitry which can control dwell time for both analog and digital signal integration. Additional "bit level" control circuitry is provided for such functions as SEM CRT blanking, and external DBC control.

The following specifications characterize the DRV-2000 SEM-PC interface hardware:

Scan control outputs: 

2 outputs, X and Y.
Resolution: 1 part in 65000.
Range and offset adjustable from -10 to + 10 volts.
Signal to noise ratio: > 90 dB.

Image digitization inputs: 

Analog Inputs: 2, typically SE and BSE
12 bit resolution.
Input range adjustable in two steps, +/- 1V range and +/- 5V range via jumpers.
input offset adjustable +/- 5V via trimpots.
Conversion time: <750 nS.
Channels are independent and capable of simultaneous digitization.

Video Signal Conditioning:

Dual gated integrators: 1 each analog input channel
8 time constants optimized over 'typical' SEM operation conditions
Automatic reset at conclusion of pixel quantization

Video Signal scaling:

PC controllable contrast: 4096 steps.
PC controllable brightness: 256 steps

Digital inputs:

Quantity 4
TTL logic level compatible
Shottky input buffered
125 nS minimum pulse width detection
16 bit counters.
Counters gated by programmable pixel dwell timer.

Pixel level data synchronization:

Two programmable serially triggered counters
DAC and scan settling timer 
'Soak' timer for quantization of signals at volume of excitation.
ADC's and digital inputs both synchronized with 'soak' timer.

Miscellaneous DBC support circuitry:

SEM CRT blanking output with jumper selectable output voltage levels.
Z brightness fixed output, trimpot settable.
DBC relay enable signal
+ 12, -12 and +5V outputs to drive DBC input of SEM.
"pass through" operation capable. For SEM's with non-standard DBC.
Jumper programmable DBC control modes 1 and 2 supported directly.
 

DIGISEMTM and DRV-2000TM are a registered trademarks of ELMDAS Company.
Questions or problems regarding this CD should be directed to: jbest@elmdas.com
Copyright © 2001 ELMDAS Co.  All rights reserved.