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

10.2.5. Transmitter Logic

The Lightweight UART transmitter consists of a 7-, 8-, or 9-bit width of TXFIFO and a corresponding 7-, 8-, or 9-bit transmit shift register. The TXFIFO can be implemented either in register with configurable depth or a fixed depth that is able to fully utilize a single memory block.

Avalon® memory-mapped host peripherals write the TXFIFO via the Avalon® memory-mapped agent port. The transmit shift register is loaded from the TXFIFO automatically if a serial transmit shift operation is not currently in progress. The transmit shift register directly feeds the TXD output. Data is shifted out to TXD LSB first.

These two registers provide double buffering. A host peripheral can write new value into the TXFIFO while the previously written character is being shifted out.

The host peripheral can monitor the status of the transmitter by reading the status registers transmit ready (TRDY), transmit data empty (TMT), and TXFIFO overrun error (TOE) bits. You are only allowed to write data to TXFIFO if the TRDY bits is HIGH, which indicates that TXFIFO is not full. Writing to TXFIFO if the TRDY bits is LOW will hit into the TXFIFO overrun error. If the overrun error occurs, TXFIFO no longer accepts subsequent write data, causing the data to be missing. The existing data that has been stored in TXFIFO will not be overwritten. The TOE bits are set and remain HIGH. The TOE bits can only be cleared by writing to the status register.

The TXFIFO filled level can be monitored by reading the value of the TXFIFO_LVL register. Note that if TXFIFO is full, the TXFIFO level rolls over to 0. Thus, the value 0 of TXFIFO_LVL can indicate either that the TXFIFO is full (that is, when the status registers transmit ready (TRDY) bit is LOW) or TXFIFO is empty.

To break data transmission, you can set the transmit break bit (TRBK) of the control register HIGH to hold TXD stream LOW. During the break condition, the transmit data that are left in TXFIFO and transmit shift register will be flushed out.

The transmitter logic automatically inserts the correct number of start, stop, and parity bits in the serial TXD data stream as required by the RS-232 specification.