Intel® Agilex™ Embedded Memory User Guide

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ID 683241
Date 4/25/2022
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Document Table of Contents
Document Table of Contents x
1. Intel® Agilex™ Embedded Memory Overview 2. Intel® Agilex™ Embedded Memory Architecture and Features 3. Intel® Agilex™ Embedded Memory Design Considerations 4. Intel® Agilex™ Embedded Memory IP References 5. Intel® Agilex™ Embedded Memory Debugging 6. Intel® Agilex™ Embedded Memory User Guide Archives 7. Document Revision History for the Intel® Agilex™ Embedded Memory User Guide
1. Intel® Agilex™ Embedded Memory Overview x
1.1. Intel® Agilex™ Embedded Memory Features
2. Intel® Agilex™ Embedded Memory Architecture and Features x
2.1. Byte Enable in Intel® Agilex™ Embedded Memory Blocks 2.2. Address Clock Enable Support 2.3. Asynchronous Clear and Synchronous Clear 2.4. Memory Blocks Error Correction Code Support 2.5. Intel® Agilex™ Embedded Memory Clocking Modes 2.6. Intel® Agilex™ Embedded Memory Configurations 2.7. Force-to-Zero 2.8. Coherent Read Memory 2.9. Freeze Logic 2.10. True Dual Port Dual Clock Emulator 2.11. Initial Value of Read and Write Address Registers 2.12. Timing/Power Optimization Feature in M20K Blocks 2.13. Intel® Agilex™ Supported Embedded Memory IPs
2.1. Byte Enable in Intel® Agilex™ Embedded Memory Blocks x
2.1.1. Byte Enable Controls 2.1.2. Data Byte Output 2.1.3. Byte Enable Behavior
2.4. Memory Blocks Error Correction Code Support x
2.4.1. Parity Bit 2.4.2. ECC Parity Flip 2.4.3. ECC Read-During-Write Behavior 2.4.4. Error Correction Code Truth Table
2.5. Intel® Agilex™ Embedded Memory Clocking Modes x
2.5.1. Single Clock Mode 2.5.2. Read/Write Clock Mode 2.5.3. Input/Output Clock Mode 2.5.4. Asynchronous/Synchronous Clears in Clocking Modes 2.5.5. Output Read Data in Simultaneous Read/Write 2.5.6. Independent Clock Enables in Clocking Modes
2.6. Intel® Agilex™ Embedded Memory Configurations x
2.6.1. Mixed-Width Port Configurations
2.8. Coherent Read Memory x
2.8.1. Forwarding Logic
3. Intel® Agilex™ Embedded Memory Design Considerations x
3.1. Consider the Memory Block Selection 3.2. Consider the Concurrent Read Behavior 3.3. Customize Read-During-Write Behavior 3.4. Consider Power-Up State and Memory Initialization 3.5. Reduce Power Consumption 3.6. Avoid Providing Non-Deterministic Input 3.7. Avoid Changing Clock Signals and Other Control Signals Simultaneously 3.8. Advanced Settings in Intel® Quartus® Prime Software for Memory
3.3. Customize Read-During-Write Behavior x
3.3.1. Same-Port Read-During-Write Mode 3.3.2. Mixed-Port Read-During-Write Mode
4. Intel® Agilex™ Embedded Memory IP References x
4.1. On Chip Memory RAM and ROM Intel® FPGA IP Cores 4.2. eSRAM Intel® Agilex™ FPGA IP 4.3. FIFO Intel® FPGA IP 4.4. Shift Register (RAM-based) Intel® FPGA IP
4.1. On Chip Memory RAM and ROM Intel® FPGA IP Cores x
4.1.1. Release Information for RAM and ROM Intel® FPGA IPs 4.1.2. RAM: 1-PORT Intel® FPGA IP Parameters 4.1.3. RAM: 2-PORT Intel® FPGA IP Parameters 4.1.4. RAM: 4-PORT Intel® FPGA IP Parameters 4.1.5. ROM: 1-PORT Intel® FPGA IP Parameters 4.1.6. ROM: 2-PORT Intel® FPGA IP Parameters 4.1.7. Changing Parameter Settings Manually 4.1.8. RAM and ROM Interface Signals
4.1.7. Changing Parameter Settings Manually x
4.1.7.1. RAM and ROM Parameter Settings
4.2. eSRAM Intel® Agilex™ FPGA IP x
4.2.1. Release Information for eSRAM Intel® Agilex™ FPGA IP 4.2.2. eSRAM System Features 4.2.3. eSRAM Intel® Agilex™ FPGA IP Parameters 4.2.4. eSRAM Intel® Agilex™ FPGA IP Interface Signals 4.2.5. eSRAM Timing Diagrams
4.2.2. eSRAM System Features x
4.2.2.1. eSRAM Specifications
4.3. FIFO Intel® FPGA IP x
4.3.1. Release Information for FIFO Intel® FPGA IP 4.3.2. Configuration Methods 4.3.3. Specifications 4.3.4. FIFO Functional Timing Requirements 4.3.5. SCFIFO ALMOST_EMPTY Functional Timing 4.3.6. FIFO Output Status Flag and Latency 4.3.7. FIFO Metastability Protection and Related Options 4.3.8. FIFO Synchronous Clear and Asynchronous Clear Effect 4.3.9. SCFIFO and DCFIFO Show-Ahead Mode 4.3.10. Different Input and Output Width 4.3.11. DCFIFO Timing Constraint Setting 4.3.12. Coding Example for Manual Instantiation 4.3.13. Design Example 4.3.14. Gray-Code Counter Transfer at the Clock Domain Crossing 4.3.15. Guidelines for Embedded Memory ECC Feature 4.3.16. FIFO Intel® FPGA IP Parameters 4.3.17. Reset Scheme
4.3.3. Specifications x
4.3.3.1. Verilog HDL Prototype 4.3.3.2. VHDL Component Declaration 4.3.3.3. VHDL LIBRARY-USE Declaration 4.3.3.4. FIFO Signals 4.3.3.5. FIFO Parameter Settings
4.3.8. FIFO Synchronous Clear and Asynchronous Clear Effect x
4.3.8.1. Recovery and Removal Timing Violation Warnings when Compiling a DCFIFO
4.3.11. DCFIFO Timing Constraint Setting x
4.3.11.1. Embedded Timing Constraint 4.3.11.2. User Configurable Timing Constraint
4.3.11.2. User Configurable Timing Constraint x
4.3.11.2.1. SDC Commands
4.4. Shift Register (RAM-based) Intel® FPGA IP x
4.4.1. Release Information for Shift Register (RAM-based) Intel® FPGA IP 4.4.2. Shift Register (RAM-based) Intel® FPGA IP Features 4.4.3. Shift Register (RAM-based) Intel® FPGA IP General Description 4.4.4. Shift Register (RAM-based) Intel® FPGA IP Parameter Settings 4.4.5. Shift Register Ports and Parameters Setting
1. Intel® Agilex™ Embedded Memory Overview
2. Intel® Agilex™ Embedded Memory Architecture and Features
3. Intel® Agilex™ Embedded Memory Design Considerations
4. Intel® Agilex™ Embedded Memory IP References
5. Intel® Agilex™ Embedded Memory Debugging
6. Intel® Agilex™ Embedded Memory User Guide Archives
7. Document Revision History for the Intel® Agilex™ Embedded Memory User Guide

4.3.14. Gray-Code Counter Transfer at the Clock Domain Crossing

This section describes the effect of the large skew between gray-code counter bits transfers at the clock domain crossing (CDC) with recommended solution. The gray-code counter is 1-bit transition occurs while other bits remain stable when transferring data from the write domain to the read domain and vice versa. If the destination domain latches on the data within the metastable range (violating setup or hold time), only 1 bit is uncertain and destination domain reads the counter value as either an old counter or a new counter. In this case, the DCFIFO still works, as long as the counter sequence is not corrupted.

The following section shows an example of how large skew between the gray-code counter bits can corrupt the counter sequence. Taking a counter width with 3-bit wide and assuming it is transferred from write clock domain to read clock domain. Assume all the counter bits have 0 delay relative to the destination clock, excluding the bit[0] that has delay of 1 clock period of source clock. That is, the skew of the counter bits will be 1 clock period of the source clock when they arrived at the destination registers.

The following shows the correct gray-code counter sequence:

000,
001,
011,
010,
110....

which then transfers the data to the read domain, and on to the destination bus registers.

Because of the skew for bit[0], the destination bus registers receive the following sequence: 

000,
000,
011,
011,
110....

Because of the skew, a 2-bit transition occurs. This sequence is acceptable if the timing is met. If the 2-bit transition occurs and both bits violate timing, it may result in the counter bus settled at a future or previous counter value, which will corrupt the DCFIFO.

Therefore, the skew must be within a certain skew to ensure that the sequence is not corrupted.

Note: Use the report_max_skew and report_net_delay reports in the Timing Analyzer for timing verification if you use the User Configurable Timing Constraint. For Embedded Timing Constraint, use the skew_report.tcl to analyze the actual skew and required skew in your design.
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