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

8.4.8. msr

Identifier Title Offset Access Reset Value Description
msr Modem Status Register 0x18 R 0x00000000 It should be noted that whenever bits 0, 1, 2 or 3 are set to logic one, to indicate a change on the modem control inputs, a modem status interrupt will be generated if enabled via the IER regardless of when the change occurred. Since the delta bits (bits 0, 1, 3) can get set after a reset if their respective modem signals are active (see individual bits for details), a read of the MSR after reset can be performed to prevent unwanted interrupts.
Bit Fields
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
dcd ri dsr cts ddcd teri ddsr dcts
Table 75.  msr Fields
Bit Name/Identifier Description Access Reset
[31:8] Reserved R 0x0
[7] Data Carrier Detect (dcd)

This bit is the complement of the modem control line (dcd_n). This bit is used to indicate the current state of dcd_n. When the Data Carrier Detect input (dcd_n) is asserted it is an indication that the carrier has been detected by the modem or data set.

R 0x0
[6] Ring Indicator (ri)

This bit is the complement of modem control line (ri_n). This bit is used to indicate the current state of ri_n. When the Ring Indicator input (ri_n) is asserted it is an indication that a telephone ringing signal has been received by the modem or data set.

R 0x0
[5] Data Set Ready (dsr)

This bit is the complement of modem control line dsr_n. This bit is used to indicate the current state of dsr_n. When the Data Set Ready input (dsr_n) is asserted it is an indication that the modem or data set is ready to establish communications with the uart.

R 0x0
[4] Clear to Send (cts)

This bit is the complement of modem control line cts_n. This bit is used to indicate the current state of cts_n. When the Clear to Send input (cts_n) is asserted it is an indication that the modem or data set is ready to exchange data with the uart.

R 0x0
[3] Delta Data Carrier Detect (ddcd)

This is used to indicate that the modem control line dcd_n has changed since the last time the MSR was read. Reading the MSR clears the DDCD bit.

Note: If the DDCD bit is not set and the dcd_n signal is asserted (low) and a reset occurs (software or otherwise), then the DDCD bit will get set when the reset is removed if the dcd_n signal remains asserted.
RC 0x0
[2] Trailing Edge of Ring Indicator (teri)

This is used to indicate that a change on the input ri_n (from an active low, to an inactive high state) has occurred since the last time the MSR was read. Reading the MSR clears the TERI bit.

RC 0x0
[1] Delta Data Set Ready (ddsr)

This is used to indicate that the modem control line dsr_n has changed since the last time the MSR was read. Reading the MSR clears the DDSR bit.

Note: If the DDSR bit is not set and the dsr_n signal is asserted (low) and a reset occurs (software or otherwise), then the DDSR bit will get set when the reset is removed if the dsr_n signal remains asserted.
RC 0x0
[0] Delta Clear to Send (dcts)

This is used to indicate that the modem control line cts_n has changed since the last time the MSR was read. Reading the MSR clears the DCTS bit.

Note: If the DCTS bit is not set and the cts_n signal is asserted (low) and a reset occurs (software or otherwise), then the DCTS bit will get set when the reset is removed if the cts_n signal remains asserted.
RC 0x0