Embedded Peripherals IP User Guide

ID 683130
Date 8/11/2025
Public
Document Table of Contents
1. Introduction 2. Avalon® -ST Single-Clock and Dual-Clock FIFO Cores 3. Avalon® -ST Serial Peripheral Interface Core 4. SPI Core 5. SPI Agent/JTAG to Avalon® Host Bridge Cores 6. Intel eSPI Agent Core 7. eSPI to LPC Bridge Core 8. Ethernet MDIO Core 9. Intel FPGA 16550 Compatible UART Core 10. UART Core 11. JTAG UART Core 12. Intel FPGA Avalon® Mailbox Core 13. Intel FPGA Avalon® Mutex Core 14. Intel FPGA Avalon® I2C (Host) Core 15. Intel FPGA I2C Agent to Avalon® -MM Host Bridge Core 16. Intel FPGA Avalon® Compact Flash Core 17. EPCS/EPCQA Serial Flash Controller Core 18. Intel FPGA Serial Flash Controller Core 19. Intel FPGA Serial Flash Controller II Core 20. Intel FPGA Generic QUAD SPI Controller Core 21. Intel FPGA Generic QUAD SPI Controller II Core 22. Interval Timer Core 23. Intel FPGA Avalon FIFO Memory Core 24. On-Chip Memory (RAM and ROM) Intel FPGA IP 25. On-Chip Memory II (RAM or ROM) Intel FPGA IP 26. Optrex 16207 LCD Controller Core 27. PIO Core 28. PLL Cores 29. DMA Controller Core 30. Modular Scatter-Gather DMA Core 31. Scatter-Gather DMA Controller Core 32. SDRAM Controller Core 33. Tri-State SDRAM Core 34. Video Sync Generator and Pixel Converter Cores 35. Intel FPGA Interrupt Latency Counter Core 36. Performance Counter Unit Core 37. Vectored Interrupt Controller Core 38. Avalon® -ST Data Pattern Generator and Checker Cores 39. Avalon® -ST Test Pattern Generator and Checker Cores 40. System ID Peripheral Core 41. Avalon® Packets to Transactions Converter Core 42. Avalon® -ST Multiplexer and Demultiplexer Cores 43. Avalon® -ST Bytes to Packets and Packets to Bytes Converter IP 44. Avalon® -ST Delay Core 45. Avalon® -ST Round Robin Scheduler Core 46. Avalon® -ST Splitter Core 47. Avalon® -MM DDR Memory Half Rate Bridge Core 48. Intel FPGA GMII to RGMII Converter Core 49. HPS GMII to RGMII Adapter Intel® FPGA IP 50. Intel FPGA MII to RMII Converter Core 51. HPS GMII to TSE 1000BASE-X/SGMII PCS Bridge Core Intel® FPGA IP 52. Intel FPGA HPS EMAC to Multi-rate PHY GMII Adapter Core 53. Intel FPGA MSI to GIC Generator Core 54. Cache Coherency Translator Intel® FPGA IP 55. Altera ACE5-Lite Cache Coherency Translator 56. Lightweight UART Core

37.7.4. Positioning the ISR in Vector Table

If have a critical ISR of small size, you can achieve the best performance by positioning the ISR code directly in the vector table. In this way, you eliminate the overhead of branching from the vector table through the HAL funnel to your ISR.This section describes how to modify the VIC Basic example software to create the VIC Table-Resident example. Use this example to ensure that you understand the steps. Then you can make the equivalent changes in your custom code.

Positioning an ISR in a vector table is an advanced and error-prone technique, not directly supported by the HAL. You must exercise great caution to ensure that the ISR code fits in the vector table entry. If your ISR overflows the vector table entry, it corrupts other entries in the vector table, and your entire interrupt handling system.

When locate your ISR in the vector table, it does not need to be registered. Do not call alt_ic_isr_register(), because it overwrites the contents of the vector table.

When the ISR is in the vector table, the HAL does not provide funnel code. Therefore, the ISR code must perform any context-switching actions normally handled by the funnel. Funnel context switching can include some or all of the following actions:

  • Saving and restoring registers
  • Managing preemption
  • Managing the stack pointer

To create the fastest possible ISR, minimize or eliminate the context-switching actions your ISR must perform by conforming to the following guidelines:

  • Write the ISR in assembly language
  • Assign a shadow register set for the ISR’s use
  • Ensure that the ISR cannot be preempted by another ISR using the same register set. By default, preemption within a register set is disabled on the Nios® II processor. You can also ensure this condition by giving the ISR exclusive access to its register set.

The VIC Table-Resident example requires modifying a BSP-generated file, altera_vic1_vector_tbl.S. If you regenerate the BSP after making these modifications, the Nios® II Software Build Tools regenerate altera_vic1_vector_tbl.S, and your changes are overwritten.