8B10B Encoder/Decoder MegaCore Function

Transcription

1 8B10B Encoder/Decoder MegaCore Function User Guide 101 Innovation Drive San Jose, CA (408) Core Version: Document Version: rev1 Document Date: December 2002

2 Copyright 8B10B Encoder/Decoder MegaCore Function User Guide Copyright 2002 Altera Corporation. All rights reserved. Altera, The Programmable Solutions Company, the stylized Altera logo, specific device designations, and all other words and logos that are identified as trademarks and/or service marks are, unless noted otherwise, the trademarks and service marks of Altera Corporation in the U.S. and other countries. All other product or service names are the property of their respective holders. Altera products are protected under numerous U.S. and foreign patents and pending applications, mask work rights, and copyrights. Altera warrants performance of its semiconductor products to current specifications in accordance with Altera s standard warranty, but reserves the right to make changes to any products and services at any time without notice. Altera assumes no responsibility or liability arising out of the application or use of any information, product, or service described herein except as expressly agreed to in writing by Altera Corporation. Altera customers are advised to obtain the latest version of device specifications before relying on any published information and before placing orders for products or services. ii Altera Corporation UG-IPED8B10B-1.2

3 About this User Guide This user guide provides comprehensive information about the Altera 8B10B Encoder/Decoder MegaCore Function. Table 1 shows the user guide revision history. Table 1. User Guide Revision History Date December 2002 November 2002 October 2002 Description Third release of this user guide. Modified the directory structure. Second release of this user guide. Modified the directory structure, added release information and device family support tables. First release of this user guide. Replaces the data sheet v Added Stratix family support, and compliance with generic framing procedure (GFP). How to Find Information The Adobe Acrobat Find feature allows you to search the contents of a PDF file. Click the binoculars toolbar icon to open the Find dialog box. Bookmarks serve as an additional table of contents. Thumbnail icons, which provide miniature previews of each page, provide a link to the pages. Numerous links, shown in green text, allow you to jump to related information. Altera Corporation iii

4 About this User Guide 8B10B Encoder/Decoder MegaCore Function User Guide How to Contact Altera For the most up-to-date information about Altera products, go to the Altera world-wide web site at For technical support on this product, go to For additional information about Altera products, consult the sources shown in Table 2. Table 2. How to Contact Altera Information Type USA & Canada All Other Locations Technical support (800) 800-EPLD (3753) (7:00 a.m. to 5:00 p.m. Pacific Time) Note: (1) You can also contact your local Altera sales office or sales representative. (408) (1) (7:00 a.m. to 5:00 p.m. Pacific Time) Product literature Altera literature services (1) (1) Non-technical customer service (800) (408) (7:30 a.m. to 5:30 p.m. Pacific Time) FTP site ftp.altera.com ftp.altera.com iv Altera Corporation

5 About this User Guide 8B10B Encoder/Decoder MegaCore Function User Guide Typographic Conventions The 8B10B Encoder/Decoder MegaCore Function User Guide uses the typographic conventions shown in Table 3. Table 3. Conventions Visual Cue Bold Type with Initial Capital Letters bold type Italic Type with Initial Capital Letters Meaning Command names, dialog box titles, checkbox options, and dialog box options are shown in bold, initial capital letters. Example: Save As dialog box. External timing parameters, directory names, project names, disk drive names, filenames, filename extensions, and software utility names are shown in bold type. Examples: f MAX, \qdesigns directory, d: drive, chiptrip.gdf file. Document titles are shown in italic type with initial capital letters. Example: AN 75: High-Speed Board Design. Italic type Internal timing parameters and variables are shown in italic type. Examples: t PIA, n + 1. Variable names are enclosed in angle brackets (< >) and shown in italic type. Example: <file name>, <project name>.pof file. Initial Capital Letters Keyboard keys and menu names are shown with initial capital letters. Examples: Delete key, the Options menu. Subheading Title References to sections within a document and titles of on-line help topics are shown in quotation marks. Example: Typographic Conventions. Courier type Signal and port names are shown in lowercase Courier type. Examples: data1, tdi, input. Active-low signals are denoted by suffix n, e.g., resetn. Anything that must be typed exactly as it appears is shown in Courier type. For example: c:\qdesigns\tutorial\chiptrip.gdf. Also, sections of an actual file, such as a Report File, references to parts of files (e.g., the AHDL keyword SUBDESIGN), as well as logic function names (e.g., TRI) are shown in Courier. 1., 2., 3., and a., b., c.,... Numbered steps are used in a list of items when the sequence of the items is important, such as the steps listed in a procedure. Bullets are used in a list of items when the sequence of the items is not important. v The checkmark indicates a procedure that consists of one step only. 1 The hand points to information that requires special attention. r The angled arrow indicates you should press the Enter key. f The feet direct you to more information on a particular topic. Altera Corporation v

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7 Contents About this User Guide... iii How to Find Information... iii How to Contact Altera... iv Typographic Conventions...v About this Core...9 Release Information...9 Device Family Support...9 Introduction...10 New in Version Features...11 Performance...11 OpenCore Evaluation...11 Getting Started...13 Hardware & Software Requirements...13 Download & Install the Core...13 Downloading the 8B10B Encoder/Decoder MegaCore Function...13 Installing the 8B10B Encoder/Decoder MegaCore Function Files B10B Encoder/Decoder Directory Structure B10B Encoder/ Decoder Tutorial...17 Create a New Quartus II Project...17 Implementing the System...18 Simulate the Design...18 Using the Visual IP Software...18 Synthesize, Compile & Place & Route...19 Using Third-Party EDA Tools for Synthesis...19 Using the Quartus II Development Tool for Compilation & Place-and-Route...19 Set Up Licensing...20 Append the License to Your license.dat File...21 Specify the Core s License File in the Quartus II Software...21 Perform Post-Route Simulation...22 Specifications...23 Functional Description...23 Disparity...24 Generic Framing Procedure...24 Character Codes...25 Altera Corporation vii

8 Contents Encoder...26 Disparity...27 Cascaded Encoding...27 Encoding Latency...28 Decoder...29 Cascaded Decoding...30 Decoding Latency...31 Signals...31 viii Altera Corporation

9 About this Core 1 Release Information Table 1 provides information about this release of the 8B10B Encoder/Decoder MegaCore function. About this Core Device Family Support Table 1. 8B10B Encoder/Decoder MegaCore Function Release Information Item Description Version Release Date December 2002 Ordering Code IP-ED8B10B Product IDs 0079 Vendor ID 6AF7 Every Altera MegaCore function offers a specific level of support to each of the Altera device families. The following list describes the three levels of support: Full The core meets all functional and timing requirements for the device family and may be used in production designs Preliminary The core meets all functional requirements, but may still be undergoing timing analysis for the device family; may be used in production designs. No support The core has no support for device family and cannot be compiled for the device family in the Quartus II software. Altera Corporation 9

10 8B10B Encoder/Decoder MegaCore Function User Guide About this Core Table 2 shows the level of support offered by the 8B10B Encoder/Decoder MegaCore function to each of the Altera device families. Table 2. Device Family Support Device Family Cyclone Stratix GX Stratix APEX II APEX 20KE & APEX 20KC APEX 20K FLEX 10K Mercury Other device families Full Full Full Full Full Full Full Full No support Support Introduction Encoders and decoders are used for physical layer coding for Gigabit Ethernet, Fibre Channel, and other applications. The 8b/10b encoder takes byte inputs, and generates a direct current (DC) balanced stream (equal number of 1s and 0s) with a maximum run length of 5. Some of the individual 10-bit codes will have an equal number of 1s and 0s, while others will have either four 1s and six 0s, or, six 1s and four 0s. In the latter case, the disparity between 1s and 0s is used as an input to the next 10-bit code generation, so that the disparity can be reversed, and maintain an overall balanced stream. For this reason, some 8-bit inputs have two valid 10-bit codes, depending on the input disparity. The Altera 8B10B Encoder/Decoder MegaCore Function is a compact, high performance core capable of encoding and decoding at Gigabit Ethernet rates (125 MHz: 1 Gbps). The core is optimized for the Cyclone, Stratix GX, Stratix, APEX II, APEX 20K, FLEX 10K, and Mercury devices. New in Version Includes the encoder rom patch files 10 Altera Corporation

11 About this Core 8B10B Encoder/Decoder MegaCore Function User Guide Features Look-up table (LUT)-based implementation of encoder Industry compatible special character coding Complies with all applicable standards, including: Institute of Electrical and Electronics Engineers, IEEE 802.3z, Media Access Control (MAC) Parameters, Physical Layer, Repeater and Management Parameters for 1000 Mb/s Operation, 1998, paragraphs to American National Standards Institute, ANSI X3.230, Fibre Channel Physical and Signaling Interface (FC-PH), International Telecommunication Union, ITU-T Recommendation G.7041, Generic Framing Procedure, October About this Core Performance Table 3 shows the resource utilization and performance of some 8B10B Encoder/Decoder MegaCore function configurations. These results were obtained using the Quartus II software version 2.1. Table 3. Resource Utilization and Performance Cyclone EP1C20F400C6 Stratix EP1S25F780C5 Device Mode Logic Elements/ Logic Cells APEX 20K EP20K30ETC144-1 Mercury EP1M120F484C7AES Flex 10K EPF10K30ETC144-1 Encoder Decoder Encoder Decoder Encoder Decoder Encoder Decoder Encoder Decoder Memory f MAX (MHz) (1) Note: (1) f MAX is for non-cascaded encoders/decoders. OpenCore Evaluation The OpenCore feature lets you test-drive Altera MegaCore functions for free using the Quartus II software. You can verify the functionality of a MegaCore function quickly and easily, as well as evaluate its size and speed, before making a purchase decision. However, you cannot generate device programming files. Altera Corporation 11

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13 Getting Started Hardware & Software Requirements The instructions in this section require the following hardware and software: A PC running the Windows 98/NT/2000 operating system; or a SUN workstation running the Solaris operating system Quartus II development tool, version 2.1 or higher Model Technology TM ModelSim -Altera simulation software, version 5.5a or higher, or Innoveda Visual IP RTL Simulation Software, version 4.3 or higher with a compatible simulator 2 Getting Started Download & Install the Core This section describes how to obtain an 8B10B Encoder/Decoder MegaCore function configuration. It explains how to install the core, and walks you through the process of implementing the configuration in a design. Before you can start using Altera MegaCore functions, you must obtain the MegaCore files and install them on your PC. The following instructions describe this process. Downloading the 8B10B Encoder/Decoder MegaCore Function If you have Internet access, you can download MegaCore functions from Altera s web site at Follow the instructions below to obtain the 8B10B Encoder/Decoder core via the Internet. If you do not have Internet access, you can obtain the core from your local Altera representative. 1. Point your web browser to 2. Choose Megafunctions from the Product Type drop-down list box. 3. Choose Communications from the Technology drop-down list box. 4. Type 8B10B in the Keyword Search box. 5. Click Go. Altera Corporation 13

14 8B10B Encoder/Decoder MegaCore Function User Guide Getting Started 6. Click the link for the Altera 8B10B Encoder/Decoder MegaCore function in the search results table. The product description web page displays. 7. Click the Free Test Drive graphic on the top right of the product description web page. 8. Fill out the registration form, read the license agreement, and click the I Agree button at the bottom of the page. 9. Follow the instructions on the 8B10B Encoder/Decoder core download and installation page to download the function and save it to your hard disk. Installing the 8B10B Encoder/Decoder MegaCore Function Files For Windows, perform the following steps: 1. Choose Run (Start menu). 2. Type <path name>\<filename>.exe, where <path name> is the location of the downloaded MegaCore function and <filename> is the filename of the function. 3. Click OK. The 8B10B Encoder/Decoder Installation dialog box appears. Follow the on-line instructions to finish installation. For Solaris systems, perform the following steps: 1. Download the core, see Downloading the 8B10B Encoder/Decoder MegaCore Function on page Decompress/untar the package, using the following commands: gunzip xxx.tar.gz; tar xvf xxx.tar 3. After you have finished installing the MegaCore files, you may have to specify the core s library directory (typically <path>/ed8b10bv1.3.2/lib) as a user library in the Quartus II software to access the core in the MegaWizard Plug-In manager. Search for User Libraries in Quartus II Help for instructions on how to add these libraries. 8B10B Encoder/Decoder Directory Structure Figure 1 on page 15 shows the directory structure that will be created when the 8B10B Encoder/Decoder is installed. 14 Altera Corporation

15 Getting Started 8B10B Encoder/Decoder MegaCore Function User Guide Figure 1. 8B10B Encoder/Decoder Directory Structure <path>/ed8b10b-v1.3.2 Continued on next page doc Contains the core documentation. lib Contains the per-configuration netlists. syn Contains the encrypted netlists for the 8B10B Encoder/Decoder core. aot1085_d0_dec8b10b/ Configuration based on parameter choices for the decoder. apex/ Altera device family supported, includes APEX 20K and APEX II. Contains the aot1085_d0_dec8b10b files:.bsf(1),.e.vqm(2), _inst.v(3), _inst.vhd(4), and dec8b10b_wrapper files:.v and.vhd. (5) flex 10k/ Altera device family supported. Contains the aot1085_d0_dec8b10b files:.bsf,.e.edf(6), _inst.v, _inst.vhd, and dec8b10b_wrapper files:.v and.vhd. mercury/ Altera device family supported. Contains the aot1085_d0_dec8b10b files:.bsf,.e.vqm, _inst.v, _inst.vhd, _inst.vhd, and dec8b10b_wrapper files:.v and.vhd.. stratix/ Altera device supported, includes Stratix, Stratix GX and Cyclone. Contains the aot1085_d0_dec8b10b files:.bsf,.e.vqm, _inst.v, _inst.vhd, and dec8b10b_wrapper files:.v and.vhd. aot1085_e0_enc8b10b/ Configuration based on parameter choices for the encoder. apex/ Altera device family supported, includes APEX 20K and APEX II. Contains the aot1085_e0_enc8b10b files:.bsf,.e.vqm, _inst.v, _inst.vhd, _inst.vhd, and enc8b10b_wrapper files:.v and.vhd. flex 10k/ Altera device family supported. Contains the aot1085_e0_enc8b10b files:.bsf,.e.edf, _inst.v, _inst.vhd, and enc8b10b_wrapper files:.v and.vhd. mercury/ Altera device family supported. Contains the aot1085_e0_enc8b10b files:.bsf,.e.vqm, _inst.v, _inst.vhd, _inst.vhd, and enc8b10b_wrapper files:.v and.vhd. aot1085_e11_enc8b10b/ Configuration based on parameter choices for the encoder. stratix/ Altera device supported, includes Stratix, Stratix GX and Cyclone. Contains the aot1085_e11_ed8b10b files:.bsf, e.vqm, _inst.v, _inst.vhd, _inst.vhd, and enc8b10b_wrapper files:.v and.vhd. 2 Getting Started Notes: (1) Symbol files for the Quartus II software used to instantiate the core into a schematic design. (2) Encrypted HDL netlist file. (3) Verilog HDL instantiation file. (4) VHDL instantiation file. (5) Wrapper files used for stand-alone simulation. (6) Encrypted electronic design interchange format (EDIF) input file. Altera Corporation 15

16 8B10B Encoder/Decoder MegaCore Function User Guide Getting Started Continued from <path>/ed8b10b-v1.3.2 sim_lib Contains the simulation models. aot1085_0_ed8b10b/ Configuration based on parameter choices. modelsim_verilog/ ModelSim-Altera Verilog HDL models aot1085_0_dec8b10b aot1085_0_enc8b10b lpm_verilog modelsim_vhdl/ ModelSim-Altera VHDL models aot1085_0_dec8b10b aot1085_0_enc8b10b lpm_vhdl visual_ip/ Innoveda Visual IP simulation models aot1085_0_dec8b10b aot1085_0_enc8b10b test/ Demonstration testbench aot1085_11_ed8b10b/ Configuration based on parameter choices. modelsim_verilog/ ModelSim-Altera Verilog HDL models aot1085_0_dec8b10b aot1085_11_enc8b10b modelsim_vhdl/ ModelSim-Altera VHDL models aot1085_0_dec8b10b aot1085_11_enc8b10b visual_ip/ Innoveda Visual IP simulation models aot1085_0_dec8b10b aot1085_11_enc8b10b test/ Demonstration testbench 16 Altera Corporation

17 Getting Started 8B10B Encoder/Decoder MegaCore Function User Guide 8B10B Encoder/ Decoder Tutorial This tutorial explains how to obtain a configuration of the Altera 8B10B Encoder/Decoder. Once you have obtained the required configuration, you can incorporate it into your overall project. To obtain a customized 8B10B Encoder/Decoder configuration enter a request at: Your customized core will be e- mailed to you as an encrypted gate level netlist and secure RTL simulation model. This tutorial consists of the following steps: Create a New Quartus II Project on page 17 Implementing the System on page 18 Simulate the Design on page 18 Synthesize, Compile & Place & Route on page 19 Set Up Licensing on page 20 Perform Post-Route Simulation on page 22 2 Getting Started Create a New Quartus II Project Before you begin, you must create a new Quartus II project. With the New Project wizard, you specify the working directory for the project, assign the project name, and designate the name of the top-level design entity. You will also specify the 8B10B Encoder/Decoder user library. To create a new project, perform the following steps: 1. Choose Altera > Quartus II <version> (Windows Start menu) to run the Quartus II software. You can also use the Quartus II Web Edition software. 2. Choose New Project Wizard (File menu). 3. Click Next in the introduction (the introduction will not display if you turned it off previously). 4. Specify the working directory for your project. 5. Specify the name of the project. 6. Click Next. 1 Steps 7 to 10 only apply to Solaris systems. 7. Click User Library Pathnames. Altera Corporation 17

18 8B10B Encoder/Decoder MegaCore Function User Guide Getting Started 8. Type <path>\ed8b10bv.1.3.2\lib\ into the Library name box, where <path> is the directory in which you installed the 8B10B Encoder/Decoder. The default installation directory is c:\megacore. 9. Click Add. 10. Click OK. 11. Click Next. 12. Click Finish. You have finished creating your new Quartus II project. Figure 1 on page 15 shows an example project directory structure. Implementing the System Once you have your custom 8B10B Encoder/Decoder, you are ready to implement it. You can use the Quartus II software or other EDA tools to create your design. Simulate the Design As shown in Figure 1 on page 15, the 8B10B MegaCore function offers two possible configurations for the encoder: _0 is optimized for APEX, FLEX 10K, and Mercury devices _11 is optimized for the Stratix family Altera provides models you can use for functional verification of the core within your design. A Verilog HDL demonstration testbench, including scripts to run it, is also provided. This demonstration testbench, used with the ModelSim-Altera simulator, demonstrates how to instantiate a model in a design. To find the simulation models for your selected configuration, refer to sim_lib directory in Figure 1. Using the Visual IP Software The Visual IP software facilitates the use of Visual IP simulation models with third-party simulation tools. To view a simulation model, you must have the Visual IP software installed on your system. To download the software, or for instructions on how to use the software, refer to the Altera web site at and search for Visual IP. For examples of how to use the provided Visual IP model, refer to the sample scripts included with the demonstration testbench. 18 Altera Corporation

19 Getting Started 8B10B Encoder/Decoder MegaCore Function User Guide Synthesize, Compile & Place & Route After you have verified that your design is functionally correct, you are ready to perform synthesis and place-and-route. Synthesis can be performed by the Quartus II development tool, or by a third-party synthesis tool. The Quartus II software works seamlessly with tools from many EDA vendors, including Cadence, Exemplar Logic TM, Mentor Graphics, Synopsys, Synplicity, and Viewlogic. Using Third-Party EDA Tools for Synthesis To synthesize your design in a third-party EDA tool, follow these steps: 1. Create your custom design instantiating an 8B10B Encoder/Decoder core. 2. Synthesize the design using your third-party EDA tool. Your EDA tool should treat the core instantiation as a black box by either setting attributes or ignoring the instantiation. 2 Getting Started 3. After compilation, generate a netlist file in your third-party EDA tool. Using the Quartus II Development Tool for Compilation & Place-and- Route To use the Quartus II software to compile and place-and-route your design, follow these steps: 1. Select Compile mode (Processing menu). 2. Specify the Compiler settings in the Compiler Settings dialog box (Processing menu) or use the Compiler Settings wizard. 3. Specify the input settings for the project. a. Choose EDA Tool Settings (Project menu). b. Select Custom EDIF in the Design entry/synthesis tool list. c. Click Settings. d. In the EDA Tool Input Settings dialog box, select the relevant tool name or option from the Design Entry/Synthesis Tool list. 4. Add your third-party EDA tool-generated netlist file to your project. Altera Corporation 19

20 8B10B Encoder/Decoder MegaCore Function User Guide Getting Started 5. Add any.tdf,.vhd, or.v files not synthesized in the third-party tool. 6. Add the pre-synthesized and encrypted.e.vqm file from your working directory, created by the MegaWizard Plug-In Manager. 7. Constrain your design as needed. 8. Compile your design. The Quartus II Compiler synthesizes and performs place-and-route on your design. f Refer to Quartus II Help for further instructions on performing compilation. Set Up Licensing After you have compiled and analyzed your design, you are ready to configure your targeted Altera FPGA device. You can use Altera s OpenCore evaluation software to compile and simulate the 8B10B Encoder/Decoder MegaCore function in the Quartus II software, allowing you to evaluate it before purchasing a license. However, you must obtain a license from Altera before you can generate programming files or EDIF, VHDL, or Verilog HDL gate-level netlist files for simulation in third-party EDA tools. After you purchase a license for the 8B10B Encoder/Decoder MegaCore Function, you can request a license file from the Altera web site at and install it on your PC. When you request a license file, Altera s you a license.dat file. If you do not have Internet access, contact your local Altera representative. To install your license, you can either append the license to your license.dat file or you can specify the core s license.dat file in the Quartus II software. 1 Before you set up licensing for the 8B10B Encoder/Decoder MegaCore Function, you must already have the Quartus II software installed on your PC, with licensing set up. 20 Altera Corporation

21 Getting Started 8B10B Encoder/Decoder MegaCore Function User Guide Append the License to Your license.dat File To append the license, perform the following steps: 1. Close the following software if it is running on your PC: Quartus II MAX+PLUS II LeonardoSpectrum TM Synplify ModelSim 2. Open the 8B10B Encoder/Decoder MegaCore Function license file in a text editor. The file should contain one FEATURE line, spanning two lines. 3. Open your Quartus II license.dat file in a text editor. 2 Getting Started 4. Copy the FEATURE line from the 8B10B Encoder/Decoder MegaCore Function license file and paste it into a new line in the Quartus II license file. 1 Do not delete any FEATURE lines from the Quartus II license file. 5. Save the Quartus II license file as a text file. 1 When using editors such as Microsoft Word or Notepad, ensure that the file does not have extra extensions appended to it after you save (e.g., license.dat.txt or license.dat.doc). Verify the filename at a command prompt. Specify the Core s License File in the Quartus II Software To specify the core s license file, perform the following steps: 1. Create a text file with the FEATURE line and save it to your hard disk. 1 Altera recommends that you give the file a unique name, e.g., <core name>_license.dat. 2. Run the Quartus II software. 3. Choose License Setup (Tools menu). The Options dialog box opens to the License Setup page. Altera Corporation 21

22 8B10B Encoder/Decoder MegaCore Function User Guide Getting Started 4. In the License file box, add a semicolon to the end of the existing license path and filename. 5. Type the path and filename of the core license file after the semicolon. 1 Do not include any spaces either around the semicolon or in the path/filename. 6. Click OK to save your changes. Perform Post-Route Simulation After you have licensed the core, you can generate EDIF, VHDL, Verilog HDL, and Standard Delay Output Files from the Quartus II software and use them with your existing EDA tools to perform functional modeling and post-routing simulation of your design. 1. Open your existing Quartus II project. 2. Depending on the type of output file you want, specify Verilog HDL output settings or VHDL output settings in the General Settings dialog box (Project menu). 3. Compile your design with the Quartus II software, refer to the Using the Quartus II Development Tool for Compilation & Placeand-Route section. The Quartus II software generates output and programming files. 4. You can now import your Quartus II software-generated output files (.edo,.vho,.vo, or.sdo) into your third-party EDA tool for postroute, device-level, and system-level simulation. 22 Altera Corporation

23 Specifications Functional Description The core consists of an encoder (ENC8B10B) and a decoder (DEC8B10B), see Figure 3 on page 24. The encoder encodes one 8-bit byte of data into a 10-bit transmission code, and the decoder decodes a 10-bit code into one 8-bit byte of data. Figure 2 illustrates the bidirectional conversion process. The eight input bits are named A, B, C, D, E, F, G, H. Bit A is the least significant bit (LSB), and bit H is the most significant bit (MSB). They are split into two groups: The five-bit group A, B, C, D, E, and the three-bit group F, G, H. The coded bits are named a, b, c, d, e, i, f, g, h, j (the order is not alphabetical). These bits are also split into two groups: the six-bit group a, b, c, d, e, i, and the four-bit group f, g, h, j. 3 Figure 2. 8b10b Conversion H G F E D C B A Specifications 8b10b Conversion j h g f i e d c b a MSB sent last LSB sent first In bit serial transmission, the LSB is usually transmitted first, while the MSB is usually transmitted last. Altera Corporation 23

24 8B10B Encoder/Decoder MegaCore Function User Guide Specifications Disparity Disparity is the difference between the number of 1s and 0s in the encoded word. Neutral disparity indicates the number of 1s and 0s are equal. Positive disparity indicates more 1s than 0s. Negative disparity indicates more 0s than 1s. The core is designed to maintain a neutral average disparity. Average disparity determines the DC component of a serial line. Running disparity is a record of the cumulative disparity of every encoded word, and is tracked by the encoder. To guarantee neutral average disparity, a positive running disparity must be followed by neutral or negative disparity; a negative running disparity must be followed by neutral or positive disparity. If these conditions are not met, the decoder flags an error by asserting its rderr output. f For details on running disparity rules, see the IEEE 802.3z specification, paragraph Generic Framing Procedure The 8B10B Encoder/Decoder core can be used within GFP applications, see Figure 3 for an example. Figure 3. 8B10B Encoder/Decoder GFP Typical Application Ingress Egress Gigabit Ethernet Stream (8B/10B Encoded) 8B/10B Decoder GFP Mapper Transport Network GFP Data Stream (64B/65B Encoded) GFP Demapper 8B/10B Encoder Gigabit Ethernet Stream (8B/10B Encoded) On ingress to the transport network, if the decoder receives an unrecognized codeword, such as an illegal codeword or a legal codeword with a running disparity error, it asserts the rderr signal. By asserting the rderr signal, the decoder indicates to the mapper that an unrecognized codeword has been received, the mapper then generates a special control character, the 10B_ERR code. In addition, the mapper remaps the 8B/10B codewords into 64B/65B codewords before sending the data to the transport network. 24 Altera Corporation

25 Specifications 8B10B Encoder/Decoder MegaCore Function User Guide On egress from the transport network, the demapper encodes the 64B/65B codewords into 8b/10B codewords before sending them to the encoder. When the encoder receives the 10B_ERR code, it sends out one of the two 10-bit illegal codewords with neutral disparity: (RD-) or (RD+), depending on the running disparity. Character Codes In addition to 256 data characters, the 8b/10b code defines thirteen out-ofband indicators, also called special control characters. The 256 data characters are named Dx.y, and the special control characters are named Kx.y except for the special code 10B_ERR (see Table 4 on page 25). The x value corresponds to the five-bit group, and the y value to the three-bit group. The special control characters indicate, for example, whether the data is idle, test data, or data delimiters. In applications where encoded characters are transmitted bit-serially, the comma character (K28.5) is usually used for alignment purposes as its 10-bit code is guaranteed not to occur elsewhere in the encoded bit stream, except after K28.7 which is normally only sent during diagnostic. Table 4 lists the special K codes used by the core. 3 Table 4. Character Codes 10-Bit Special K Codes Equivalent 8-Bit Codes K b000_11100 K b001_11100 K b010_11100 K b011_11100 K b100_11100 K28.5 (1) 8 b101_11100 K b110_11100 K b111_11100 K b111_10111 K b111_11011 K b111_11101 K b111_ B_ERR 8 b111_11111 Specifications Note: (1) K28.5 is a comma character used for alignment purposes, and to represent the IDLE code. Altera Corporation 25

26 8B10B Encoder/Decoder MegaCore Function User Guide Specifications Encoder The encoder uses an innovative, proprietary, non-partitioned, memorybased LUT implementation to convert data and identified special 8-bit codes from 8 bits to 10 bits. See Figure 2 on page 23 for an illustration of the conversion process. To encode an 8-bit word, the 8-bit value must be applied to the datain inputs and the enable input must be asserted (active high). When one of the thirteen special 10-bit codes is to be inserted, the equivalent 8-bit code is placed on the datain lines and the kin input is asserted. The core performs error checking to ensure the out-of-band 8-bit code is valid. If not, the kerr output is asserted. See Table 4 on page 25 for a list of the valid K codes. Idle (K28.5) characters can be automatically inserted when enable is not asserted by asserting the idle_ins input. The encoder encodes invalid characters in the same way it encodes Idle (K28.5) codes. The decoder treats invalid characters as Idle codes. Figure 4 shows a block diagram of the encoder. Figure 4. Encoder clk reset_n kin enable idle_ins datain [7:0] rdin rdforce kerr dataout [9:0] valid rdout rdcascade 26 Altera Corporation

27 Specifications 8B10B Encoder/Decoder MegaCore Function User Guide Disparity The running disparity can be forced to positive or negative, allowing the user to insert a special resynchronization pattern, or disparity errors. When the rdforce input is asserted, the value on the rdin port is assumed to be the current running disparity. Setting rdin to 0 forces the encoder to produce an encoded word with positive or neutral disparity. Setting rdin to 1 forces the encoder to produce an encoded word with negative or neutral disparity. Cascaded Encoding Two encoders can be cascaded to allow for 16-bit word encoding. The encoders are cascaded by connecting the rdcascade output of the most significant byte (MSByte) encoder to the rdin input of the least significant byte (LSByte) encoder, and by connecting the rdout output of the LSByte encoder to the rdin input of the MSByte encoder. These connections ensure proper running disparity computation. The rdforce inputs must be asserted (active high) for the encoders to take into account the value on the rdin inputs, rather than use their internally generated running disparity. Both enable inputs must be high or low at the same time. The kin [1] signal relates to datain[15:8], and kin[0] relates to datain[7:0]. Figure 5 on page 28 shows two encoders connected together to perform cascaded encoding. 3 Specifications Altera Corporation 27

28 8B10B Encoder/Decoder MegaCore Function User Guide Specifications Figure 5. Cascaded Encoding Note (1) clk kin [1:0] datain [15:0] reset_n kin [1] enable idle_ins datain [15:8] rdin kerr dataout [9:0] valid rdout rdcascade rdforce clk reset_n kin [0] enable idle_ins datain [7:0] rdin rdforce kerr dataout [9:0] valid rdout rdcascade Note: (1) The enable, idle_ins, and rdforce signals are set high (logic 1). Encoding Latency The encoder is pipelined, thus it takes three clock cycles for a character to be encoded. The encoded value corresponding to the values of datain and kin sampled by the encoder on rising edge n is output shortly after rising edge n+2, and is available to be sampled on the rising edge of clock cycle n+3. (See Figure 6 on page 29). To enable cascaded encoding, the data paths fed by the rdforce and rdin inputs are not pipelined. Since rdforce and rdin are normally only used in cascaded configurations, this should not be a problem. 28 Altera Corporation

29 Specifications 8B10B Encoder/Decoder MegaCore Function User Guide In cases where the rdforce and rdin inputs are to be used in noncascaded configurations, they should be delayed two clock cycles with respect to their corresponding datain and kin values. This can be achieved by inserting two registers in series with each of the inputs to be delayed, the following example Verilog HDL code shows how to implement the required delay registers. Example: Adding delay to rdforce and rdin for non-cascaded applications: // The _pre2 registers are set at the same time as datain and kin. reg rdforce_pre2; reg rdin_pre2; // The _pre1 registers provide an extra clock tick of delay reg rdforce_pre1; reg rdin_pre1; (posedge clk) begin rdforce <= rdforce_pre1; rdforce_pre1 <= rdforce_pre2; rdin <= rdin_pre1; rdin_pre1 <= rdin_pre2; end Figure 6. Encoder Timing Diagram n n+1 n+2 n+3 3 Specifications clk datain, kin, enable a b c d e f g dataout a b c d rdforce, rdin a b c d e Decoder Data and identified 10-bit special K codes are converted from 10 bits to 8 bits; see Table 4 on page 25 for a list of the valid K codes, and Figure 2 on page 23 for an illustration of the conversion process. Altera Corporation 29

30 8B10B Encoder/Decoder MegaCore Function User Guide Specifications When special 10-bit K codes are received, the special K codes are translated to 8-bit values, and the kout signal is asserted. The decoder also checks for invalid 10-bit codes. When the decoder receives an invalid code, it asserts the kerr signal and decodes the value to an arbitrary number, according to the rules for decoding valid codes. When the idle_del signal is asserted, it deletes all 10-bit words identified as the special IDLE character of K28.5. When the receiver detects a disparity error, the rderr signal is asserted. Figure 7 shows a block diagram of the decoder. Figure 7. Decoder clk reset_n idle_del enable datain [9:0] rdin rdforce valid dataout [7:0] kout kerr rderr rdout rdcascade Cascaded Decoding Two decoders can be cascaded to decode two words simultaneously. The decoders are cascaded in a similar fashion as the encoders by connecting the rdcascade output of the first decoder to the rdin input of the second decoder, and by connecting the rdout output of the second decoder to the rdin input of the first decoder. The rdforce inputs of both decoders must be tied high. To enable cascaded decoding, the data paths fed by the rdin and rdforce inputs are not cascaded. If these inputs are to be used in noncascaded decoders, they should be delayed by one clock cycle with respect to their corresponding datain and kin inputs. 30 Altera Corporation

31 Specifications 8B10B Encoder/Decoder MegaCore Function User Guide Decoding Latency The decoder is pipelined, thus it takes two clock cycles for a character to be decoded. The decoded value corresponding to the value of datain sampled by the decoder on rising edge n is output shortly after rising edge n+1, and is available to be sampled on the rising edge of clock cycle n+2. (See Figure 6 on page 29). Figure 8. Decoder Timing Diagram n n+1 n+2 n+3 clk datain, enable a b c d e f g dataout, kout, kerr, rdout, rderr a b c d e 3 Signals rdforce, rdin a b c d e f Tables 5 and 6 list the signals for the encoder and decoder. Specifications Table 5. Encoder Signals (Part 1 of 2) Signal Name Direction Description clk Input Clock. The input is latched, and the result is output on this clock. There is a three clock cycle latency between the input and output. reset_n Input Active low, reset. Asynchronously resets all registers in the core. kin Input Command byte indicator. When high, indicates that the input is a command byte, not a data byte. enable Input Enable encoder signal. When high, indicates that the data currently present on the datain input is to be encoded. idle_ins Input Idle character insert. When high, idle (K28.5) characters are inserted when enable is not asserted. datain[7:0] Input Data input. This is the 8-bit input word, data or command. rdin Input Running disparity input. When rdforce is high, the value on this pin is used as the current running disparity instead of the internally generated one. Altera Corporation 31

32 8B10B Encoder/Decoder MegaCore Function User Guide Specifications Table 5. Encoder Signals (Part 2 of 2) Signal Name Direction Description rdforce Input Force running disparity. When high, the rdin value overrides the internally generated running disparity. kerr Output Special K character error. This signal is set high when enable and kin are high and the value on datain is not a valid special K character. dataout[9:0] Output Data output. This is the 10-bit encoded output. valid Output Valid signal. When high, indicates that a valid encoded word is present on the dataout output. rdout Output Running disparity output. The current running disparity (after encoding the word present on the dataout output). rdcascade Output Cascaded Running disparity. Used when encoders are cascaded. Table 6. Decoder Signals Signal Name Direction Description clk Input Clock. The input is latched, and the result output on this clock. There is a three clock cycle latency between the input and output. reset_n Input Active low, reset. Asynchronously resets all registers in the core. idle_del Input Idle delete signal. When high, idle words (K28.5) are removed from the stream (i.e. valid is set low when idle words are received). enable Input Enable decoder signal. When high, indicates that the data currently present on the datain input is to be decoded. datain[9:0] Input Data input. This is the 10-bit encoded input word. rdin Input Running disparity input. When rdforce is high, the value on this pin is used as the current running disparity instead of the internally generated one. rdforce Input Force running disparity. When high, the rdin value overrides the internally generated running disparity. valid Output Valid signal. When high, indicates that a valid decoded word is present on the dataout output. dataout[7:0] Output Data output. This is the 8-bit decoded data or command. kout Output Command output. When high, indicates that the output is a command byte, not a data byte. kerr Output Special K error. Asserted high when an invalid 10-bit word is received. rderr Output Running disparity error. When high indicates the running disparity rules have been violated. rdout Output Running disparity output. The current running disparity (after decoding the word present on the dataout output). rdcascade Output Cascaded Running disparity. Used when decoders are cascaded. 32 Altera Corporation