High Speed Data Acquisition Architectures

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High Speed Data Acquisition Architectures
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Some Basic Architectures

• Non-Buffered (streaming)
• FIFO Buffered
• Multiplexed RAM
• Ping Pong Multiplexed RAM
• Dual Port RAM

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Streaming Interface Block Diagram
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Advantages / Disadvantages of Streaming

• Advantages
• Simple, low cost
• If only a small sample block is required,
  internal DSP RAM can be used for buffering
• Processing takes place in real time
• Disadvantages
• Limited sampling speed

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FIFO Buffered Block Diagram
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Advantages / Disadvantages of FIFO Buffered

• Advantages
• Simple
• Allows initial samples to be processed while
  subsequent samples are collected
• Moderate cost, low to moderate density
• Fast 100MHz clock rates readily available
• Disadvantages
• Sequential access, unneeded samples must be
  unloaded
• Calculations cannot be done in place

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Multiplexed RAM Block Diagram
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Advantages / Disadvantages of Multiplexed RAM

• Advantages
• Low cost
• High density
• Random access
• Calculations can be done in place
• Disadvantages
• More complex than FIFO, requires multiplexers,
  counters, etc
• RAM only available after all data has been
  collected. Processing of first samples cannot
  proceed in parallel with subsequent data
  collection
• RAM access time may require that ADC data be
  demultiplexed into multiple data streams

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Ping Pong Multiplexed RAM Block Diagram
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Advantages / Disadvantages of Ping Pong
Multiplexed RAM

• Advantages
• High density
• Random access
• One data buffer is always available to DSP/Host,
  so next data set is collected while first data
  set is processed
• Calculations can be done in place
• Disadvantages
• Complex, requires dual RAM banks, several
  multiplexers, counters, etc
• RAM access time may require that ADC data be
  demultiplexed into multiple data streams

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Dual Port RAM Block Diagram
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Advantages / Disadvantages of Dual Port RAM

• Advantages
• Simple
• Random access
• First data point is available for processing
  immediately
• Calculations can be done in place
• Disadvantages
• Low density, high cost
• RAM access time may require that ADC data be
  demultiplexed into multiple data streams

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Interfaces

• USB 2.0
• 10/100 LAN
• Gigabit LAN
• Parallel Bus (PXI, CPCI, VME, VXI, etc)

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USB 2.0

• Advantages
• Simple hardware
• 480 Mbps
• Widely available on desktops and laptops
• Disadvantages
• Can require substantial software overhead
• Sharing bus with over devices limits bandwidth
• Must be in close proximity to computer

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10/100 LAN

• Advantages
• Widely available on desktops and laptops
• Operates over long distances
• Disadvantages
• Typically requires coprocessor
• Can require substantial software overhead
• Sharing bus with other devices limits bandwidth

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Gigabit LAN

• Advantages
• 1000 Mbps
• Operates over long distances
• Disadvantages
• Typically requires embedded SBC with operating
  system support
• Can require substantial software overhead
• Sharing bus with other devices limits bandwidth

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Parallel Bus

• Advantages
• Fastest possible data transfer
• DSP may not be required for some applications
• Can use off the shelf SBC as controller/host
  processor
• Host processor/OS could support other interfaces
  (e.g. Gigabit LAN)
• Disadvantages
• Expensive (requires SBC)
• Size, power consumption

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ADC14100-USB Block Diagram
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ADC14100-USB Front Panel
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ADC14100-USB Rear Panel
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ADC14100-USB Features

• 14 Bit 100 MSPS ADC
• Analog Devices ADSP-21262 DSP
• 256K x 18, 100 MHz FIFO memory
• USB 2.0 Interface
• RS232 Interface
• Hardware decimator for lower sample rates at full
  analog bandwidth
• 3 software selectable clock sources
• Internal 100 MHz oscillator
• Internal 80 MHz oscillator
• External clock