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Chapter 4: Designing with the Core

deasserted on the next clock cycle. The Sink FIFO read logic should then evaluate the SnkFFEmpty_n signal to verify that there is no data in the FIFO in case an additional word was simultaneously written into the FIFO. An example of this is provided with the SPI-4.2 Lite core in the Design Example (see the pl4_lite_fifo_loopback_read.v/vhd file.) This example also illustrates the Sink FIFO Valid signal, which is asserted while there is valid data on the data bus.

SnkFFClk

SnkFFRdEn_n

SnkFFValid

SnkFFData

SnkFFAlmostEmpty_n

SnkFFEmpty_n

Figure 4-4:Sink FIFO Almost Empty

Sink FIFO Empty

Figure 4-5. illustrates the behavior of the Empty (SnkFFEmpty_n) status signal. As shown in the waveform, the empty flag is asserted with the last word read out of the FIFO. In this example, the Almost Empty flag is asserted prior to a read access being initiated. In this case, there is one data word remaining in the FIFO. To access this word, assert the Sink FIFO Read Enable (SnkFFRdEn_n) signal for one cycle.

SnkFFClk

SnkFFRdEn_n

SnkFFValid

SnkFFData

SnkFFAlmostEmpty_n

SnkFFEmpty_n

Figure 4-5:Sink FIFO Empty

Sink Almost Full

The behavior of Sink Almost Full flag (SnkAlmostFull_n) is dependent on the static configuration signals SnkAFThresAssert and SnkAFThresNegate. When the SnkAlmostFull_n flag is asserted, SnkAFThresAssert specifies the number of empty FIFO locations available. For a 64-bit user interface, each FIFO location can contain up to 1/2 of a credit (8 bytes) worth of data from a single packet. For a 32-bit user interface, each FIFO location can contain up to 1/4 of a credit (4 bytes) worth of data from a single packet. SnkAFThresNegate specifies when the SnkAlmostFull_n flag is deasserted.

The number of bytes that can be written into the Sink SPI-4.2 interface after the Sink

Almost Full flag is asserted depends on received packet sizes, data patterns, and

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SPI-4.2 Lite v4.3 User Guide

 

 

UG181 June 27, 2008

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UG181 specifications

Xilinx UG181 refers to the User Guide for the Xilinx 7 Series FPGAs, which offers a comprehensive overview of the architecture, capabilities, and features of these powerful field-programmable gate arrays (FPGAs). Designed to cater to a wide range of applications, Xilinx 7 Series FPGAs are widely adopted in industries such as telecommunications, automotive, aerospace, and consumer electronics.

One of the main features of the Xilinx 7 Series FPGAs is their use of advanced 28nm technology, which enables them to achieve high performance while maintaining low power consumption. This fine process technology not only ensures better power efficiency but also allows for increased logic density. The 7 Series includes several families, such as Artix-7, Kintex-7, and Virtex-7, each tailored for specific application demands ranging from cost-sensitive solutions to high-performance data processing.

Xilinx 7 Series FPGAs also incorporate a rich set of programmable logic resources. This includes Look-Up Tables (LUTs), Flip-Flops, and Digital Signal Processing (DSP) slices that have been optimized for various arithmetic functions. With several thousands of logic cells available, designers can implement complex algorithms and systems directly in hardware for improved performance over traditional software solutions.

In addition to their logic capabilities, Xilinx 7 Series FPGAs feature an array of high-speed serial communication interfaces. These include support for technologies like PCI Express, Gigabit Ethernet, and Serial RapidIO, which facilitate efficient data transfer and integration into enterprise-level systems. The presence of high-speed transceivers also makes them ideal for applications that require fast data handling like video processing or high-frequency trading.

Furthermore, these FPGAs offer extensive memory options, including support for a wide range of external memory interfaces. This versatility allows for the integration of high-bandwidth memory solutions, which is essential for performance-intensive applications. With the introduction of the Memory Controller IP, users can easily connect various memory types, ensuring flexibility in system design.

Finally, Xilinx has made significant strides in development tools for 7 Series FPGAs, providing a robust ecosystem for design engineers. With design suites such as Vivado and SDK, users benefit from a comprehensive platform for deciding, simulating, and implementing designs efficiently. The combination of advanced hardware capabilities and powerful software tools solidifies the position of Xilinx 7 Series FPGAs as a preferred choice for custom digital hardware design across various industries.
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