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    • 參數(shù)資料
      型號: XCS05XL-3PC84I
      廠商: XILINX INC
      元件分類: FPGA
      英文描述: Spartan and Spartan-XL Families Field Programmable Gate Arrays
      中文描述: FPGA, 100 CLBS, 2000 GATES, PQCC84
      封裝: PLASTIC, LCC-84
      文件頁數(shù): 18/66頁
      文件大小: 809K
      代理商: XCS05XL-3PC84I
      R
      Spartan and Spartan-XL Families Field Programmable Gate Arrays
      4-18
      DS060 (v1.5) March 2, 2000
      On-Chip Oscillator
      Spartan/XL devices include an internal oscillator. This
      oscillator is used to clock the power-on time-out, for config-
      uration memory clearing, and as the source of CCLK in
      Master configuration mode. The oscillator runs at a nominal
      8 MHz frequency that varies with process, V
      CC
      , and tem-
      perature. The output frequency falls between 4 MHz and
      10 MHz.
      The oscillator output is optionally available after configura-
      tion. Any two of four resynchronized taps of a built-in divider
      are also available. These taps are at the fourth, ninth, four-
      teenth and nineteenth bits of the divider. Therefore, if the
      primary oscillator output is running at the nominal 8 MHz,
      the user has access to an 8-MHz clock, plus any two of
      500 kHz, 16 kHz, 490 Hz and 15 Hz. These frequencies
      can vary by as much as -50% or +25%.
      These signals can be accessed by placing the OSC4
      library element in a schematic or in HDL code. The oscilla-
      tor is automatically disabled after configuration if the OSC4
      symbol is not used in the design.
      Global Signals: GSR and GTS
      Global Set/Reset
      A separate Global Set/Reset line, as shown in
      Figure 3 on
      page 4
      for the CLB and
      Figure 6 on page 5
      for the IOB, sets
      or clears each flip-flop during power-up, reconfiguration, or
      when a dedicated Reset net is driven active. This global net
      (GSR) does not compete with other routing resources; it
      uses a dedicated distribution network.
      Each flip-flop is configured as either globally set or reset in
      the same way that the local set/reset (SR) is specified.
      Therefore, if a flip-flop is set by SR, it is also set by GSR.
      Similarly, if in reset mode, it is reset by both SR and GSR.
      GSR can be driven from any user-programmable pin as a
      global reset input. To use this global net, place an input pad
      and input buffer in the schematic or HDL code, driving the
      GSR pin of the STARTUP symbol. (See
      Figure 19
      .) A spe-
      cific pin location can be assigned to this input using a LOC
      attribute or property, just as with any other user-program-
      mable pad. An inverter can optionally be inserted after the
      input buffer to invert the sense of the GSR signal. Alterna-
      tively, GSR can be driven from any internal node.
      Global 3-State
      A separate Global 3-state line (GTS) as shown in
      Figure 5
      on page 6
      forces all FPGA outputs to the high-impedance
      state, unless boundary scan is enabled and is executing an
      EXTEST instruction. GTS does not compete with other
      routing resources; it uses a dedicated distribution network.
      GTS can be driven from any user-programmable pin as a
      global 3-state input. To use this global net, place an input
      pad and input buffer in the schematic or HDL code, driving
      the GTS pin of the STARTUP symbol. This is similar to what
      is shown in
      Figure 19
      for GSR except the IBUF would be
      connected to GTS. A specific pin location can be assigned
      to this input using a LOC attribute or property, just as with
      any other user-programmable pad. An inverter can option-
      ally be inserted after the input buffer to invert the sense of
      the Global 3-state signal. Alternatively, GTS can be driven
      from any internal node.
      Boundary Scan
      The "bed of nails" has been the traditional method of testing
      electronic assemblies. This approach has become less
      appropriate, due to closer pin spacing and more sophisti-
      cated assembly methods like surface-mount technology
      and multi-layer boards. The IEEE Boundary Scan Standard
      1149.1 was developed to facilitate board-level testing of
      electronic assemblies. Design and test engineers can
      embed a standard test logic structure in their device to
      achieve high fault coverage for I/O and internal logic. This
      structure is easily implemented with a four-pin interface on
      any boundary scan compatible device. IEEE 1149.1-com-
      patible devices may be serial daisy-chained together, con-
      nected in parallel, or a combination of the two.
      The Spartan and Spartan-XL families implement IEEE
      1149.1-compatible BYPASS, PRELOAD/SAMPLE and
      EXTEST boundary scan instructions. When the boundary
      scan configuration option is selected, three normal user I/O
      pins become dedicated inputs for these functions. Another
      user output pin becomes the dedicated boundary scan out-
      put. The details of how to enable this circuitry are covered
      later in this section.
      By exercising these input signals, the user can serially load
      commands and data into these devices to control the driv-
      ing of their outputs and to examine their inputs. This
      method is an improvement over bed-of-nails testing. It
      avoids the need to over-drive device outputs, and it reduces
      the user interface to four pins. An optional fifth pin, a reset
      for the control logic, is described in the standard but is not
      implemented in the Spartan/XL devices.
      The dedicated on-chip logic implementing the IEEE 1149.1
      functions includes a 16-state machine, an instruction regis-
      ter and a number of data registers. The functional details
      can be found in the IEEE 1149.1 specification and are also
      discussed in the Xilinx application note: "
      Boundary Scan in
      FPGA Devices
      ."
      PAD
      IBUF
      GSR
      GTS
      CLK DONEIN
      Q1Q4
      Q2
      Q3
      STARTUP
      X5260
      Figure 19: Schematic Symbols for Global Set/Reset
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