Embedded Peripherals IP User Guide

ID 683130
Date 10/24/2025
Public
Document Table of Contents
1. Introduction 2. Avalon® -ST Serial Peripheral Interface Core 3. SPI Core 4. SPI Agent/JTAG to Avalon® Host Bridge Cores 5. Intel eSPI Agent Core 6. eSPI to LPC Bridge Core 7. Ethernet MDIO Core 8. Intel FPGA 16550 Compatible UART Core 9. UART Core 10. Lightweight 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. EPCS/EPCQA Serial Flash Controller Core 17. Intel FPGA Serial Flash Controller Core 18. Intel FPGA Serial Flash Controller II Core 19. Intel FPGA Generic QUAD SPI Controller Core 20. Intel FPGA Generic QUAD SPI Controller II Core 21. Interval Timer Core 22. Intel FPGA Avalon FIFO Memory Core 23. On-Chip Memory (RAM and ROM) Intel FPGA IP 24. On-Chip Memory II (RAM or ROM) Intel FPGA IP 25. PIO Core 26. PLL Cores 27. DMA Controller Core 28. Modular Scatter-Gather DMA Core 29. Scatter-Gather DMA Controller Core 30. Video Sync Generator and Pixel Converter Cores 31. Intel FPGA Interrupt Latency Counter Core 32. Performance Counter Unit Core 33. Vectored Interrupt Controller Core 34. System ID Peripheral Core 35. Intel FPGA GMII to RGMII Converter Core 36. HPS GMII to RGMII Adapter IP 37. Intel FPGA MII to RMII Converter Core 38. HPS GMII to TSE 1000BASE-X/SGMII PCS Bridge Core IP 39. Intel FPGA HPS EMAC to Multi-rate PHY GMII Adapter Core 40. Intel FPGA MSI to GIC Generator Core 41. Cache Coherency Translator IP 42. Altera ACE5-Lite Cache Coherency Translator

3.4.3.2. txdata Register

A host peripheral writes data to be transmitted into the txdata register. When the status register's TRDY bit is 1, it indicates that the txdata register is ready for new data. The TRDY bit is set to 0 whenever the txdata register is written. The TRDY bit is set to 1 after data is transferred from the txdata register into the transmitter shift register, which readies the txdata holding register to receive new data.

A host peripheral should not write to the txdata register until the transmitter is ready for new data. If TRDY is 0 and a host peripheral writes new data to the txdata register, a transmit-overrun error occurs and the status register's TOE bit is set to 1. In this case, the new data is ignored, and the content of txdata remains unchanged.

As an example, assume that the SPI core is idle (that is, the txdata register and transmit shift register are empty), when a CPU writes a data value into the txdata holding register. The TRDY bit is set to 0 momentarily, but after the data in txdata is transferred into the transmitter shift register, TRDY returns to 1. The CPU writes a second data value into the txdata register, and again the TRDY bit is set to 0. This time the shift register is still busy transferring the original data value, so the TRDY bit remains at 0 until the shift operation completes. When the operation completes, the second data value is transferred into the transmitter shift register and the TRDY bit is again set to 1.