hw/ip/i2c/data/i2c.hjson

// Copyright lowRISC contributors.
// Licensed under the Apache License, Version 2.0, see LICENSE for details.
// SPDX-License-Identifier: Apache-2.0

{ name: "i2c"
  clock_primary: "clk_i"
  bus_interfaces: [
    { protocol: "tlul", direction: "device" }
  ],
  // INPUT pins
  available_inout_list: [
    { name: "sda", desc: "Serial input data bit" }
    { name: "scl", desc: "Serial input clock bit" }
  ]
  // INTERRUPT pins
  interrupt_list: [
    { name: "fmt_watermark"
      desc: "raised when the FMT FIFO depth falls below the low watermark."
    }
    { name: "rx_watermark"
      desc: "raised if the RX FIFO is past the high watermark."
    }
    { name: "fmt_overflow"
      desc: "raised if the FMT FIFO has overflowed."
    }
    { name: "rx_overflow"
      desc: "raised if the RX FIFO has overflowed."
    }
    { name: "nak"
      desc: "raised if there is no ACK in response to an address or data write"
    }
    { name: "scl_interference"
      desc: "raised if the SCL line drops early (not supported without clock synchronization)."
    }
    { name: "sda_interference"
      desc: "raised if the SDA line goes low when host is trying to assert high"
    }
    { name: "stretch_timeout"
      desc: "raised if target stretches the clock beyond the allowed timeout period"
    }
    { name: "sda_unstable"
      desc: "raised if the target does not assert a constant value of SDA during transmission."
    }
    { name: "trans_complete"
      desc: "raised if the host terminates the transaction by issuing STOP or repeated START."
    }
    { name: "tx_empty"
      desc: "raised if the target needs data to transmit and TX FIFO is empty."
    }
    { name: "tx_nonempty"
      desc: "raised if there are extra bytes left in TX FIFO at the end of a read."
    }
    { name: "tx_overflow"
      desc: "raised if TX FIFO has overflowed."
    }
    { name: "acq_overflow"
      desc: "raised if ACQ FIFO has overflowed."
    }
    { name: "ack_stop"
      desc: "raised if STOP is received after ACK (host sends both signals)."
    }
    { name: "host_timeout"
      desc: "raised if the host stops sending the clock during an ongoing transaction."
    }
  ]

  // REGISTER definition
  regwidth: "32"
  registers: [
    // CTRL register
    { name: "CTRL"
      desc: "I2C control register (Functions TBD)"
      swaccess: "rw"
      hwaccess: "hro"
      fields: [
        { bits: "0"
          resval: "0"
          name: "ENABLEHOST"
          desc: '''
                Enable Host I2C functionality
                '''
        }
        { bits: "1"
          resval: "0"
          name: "ENABLETARGET"
          desc: '''
                Enable Target I2C functionality
                '''
        }
        { bits: "2"
          resval: "0"
          name: "LLPBK"
          desc: '''
                Enable I2C line loopback test
                If line loopback is enabled, the internal design sees ACQ and RX data as "1"
                '''
          tags: [// Exclude from write-checks: writing 1'b1 to this bit causes interrupts unexpectedly asserted
                "excl:CsrAllTests:CsrExclWrite"]
        }
      ]
    }
    { name:     "STATUS"
      desc:     "I2C live status register"
      swaccess: "ro"
      hwaccess: "hwo"
      hwext:    "true"
      fields: [
        { bits: "0"
          name: "FMTFULL"
          desc: "FMT buffer is full"
        }
        { bits: "1"
          name: "RXFULL"
          desc: "RX buffer is full"
        }
        { bits: "2"
          name: "FMTEMPTY"
          desc: "FMT FIFO is empty"
          resval: "1"
        }
        { bits: "5"
          name: "RXEMPTY"
          desc: "RX FIFO is empty"
          resval: "1"
        }
        { bits: "3"
          name: "HOSTIDLE"
          desc: "Host functionality is idle. No Host transaction is in progress"
          resval: "1"
        }
        { bits: "4"
          name: "TARGETIDLE"
          desc: "Target functionality is idle. No Target transaction is in progress"
          resval: "1"
        }
        { bits: "6"
          name: "TXFULL"
          desc: "TX FIFO is full"
        }
        { bits: "7"
          name: "ACQFULL"
          desc: "ACQ FIFO is full"
        }
        { bits: "8"
          name: "TXEMPTY"
          desc: "TX FIFO is empty"
          resval: "1"
        }
        { bits: "9"
          name: "ACQEMPTY"
          desc: "ACQ FIFO is empty"
          resval: "1"
        }
      ]
      tags: [// Updated by the hw. Exclude from write-checks.
             "excl:CsrNonInitTests:CsrExclWriteCheck"]
    }
    { name: "RDATA"
      desc: "I2C read data"
      swaccess: "ro"
      hwaccess: "hrw"
      hwext: "true"
      hwre: "true"
      fields: [
        {bits: "7:0"}
      ]
      tags: [// Updated by the hw. Exclude from init and write-checks.
             "excl:CsrAllTests:CsrExclCheck"]
    }
    { name: "FDATA"
      desc: "I2C Format Data"
      swaccess: "wo"
      hwaccess: "hro"
      hwqe: "true"
      fields: [
        { bits: "7:0"
          name: "FBYTE"
          desc: "Format Byte. Directly transmitted if no flags are set."
        }
        { bits: "8"
          name: "START"
          desc: "Issue a START condition before transmitting BYTE."
        }
        { bits: "9"
          name: "STOP"
          desc: "Issue a STOP condition after this operation"
        }
        { bits: "10"
          name: "READ"
          desc: "Read BYTE bytes from I2C. (256 if BYTE==0)"
        }
        { bits: "11"
          name: "RCONT"
          desc: "Do not NAK the last byte read, let the read operation continue"
        }
        { bits: "12"
          name: "NAKOK"
          desc: "Do not signal an exception if the current byte is not ACK'd"
        }
      ]
    }
    { name: "FIFO_CTRL"
      desc: "I2C FIFO control register"
      swaccess: "rw"
      hwaccess: "hro"
      hwqe: "true"
      fields: [
        { bits: "0"
          swaccess: "wo"
          name: "RXRST"
          desc: "RX fifo reset. Write 1 to the register resets RX_FIFO. Read returns 0"
        }
        { bits: "1"
          swaccess: "wo"
          name: "FMTRST"
          desc: "FMT fifo reset. Write 1 to the register resets FMT_FIFO. Read returns 0"
        }
        { bits: "4:2"
          name: "RXILVL"
          desc: '''Trigger level for RX interrupts. If the FIFO depth exceeds
                this setting, it raises rx_watermark interrupt.
                '''
          enum: [
            { value: "0",
              name: "rxlvl1",
              desc: "1 character"
            },
            { value: "1",
              name: "rxlvl4",
              desc: "4 characters"
            },
            { value: "2",
              name: "rxlvl8",
              desc: "8 characters"
            },
            { value: "3",
              name: "rxlvl16",
              desc: "16 characters"
            },
            { value: "4",
              name: "rxlvl30",
              desc: "30 characters"
            },
          ]
        }
        { bits: "6:5"
          name: "FMTILVL"
          desc: '''Trigger level for FMT interrupts. If the FIFO depth falls below
                this setting, it raises fmt_watermark interrupt.
                '''
          enum: [
            { value: "0",
              name: "fmtlvl1"
              desc: "1 character"
            },
            { value: "1",
              name: "fmtlvl4",
              desc: "4 characters"
            },
            { value: "2",
              name: "fmtlvl8",
              desc: "8 characters"
            },
            { value: "3",
              name: "fmtlvl16",
              desc: "16 characters"
            }
          ]
        }
        { bits: "7"
          swaccess: "wo"
          name: "ACQRST"
          desc: "ACQ FIFO reset. Write 1 to the register resets it. Read returns 0"
        }
        { bits: "8"
          swaccess: "wo"
          name: "TXRST"
          desc: "TX FIFO reset. Write 1 to the register resets it. Read returns 0"
        }
      ]
    }
    { name: "FIFO_STATUS"
      desc: "I2C FIFO status register"
      swaccess: "ro"
      hwaccess: "hwo"
      hwext: "true"
      fields: [
        { bits: "5:0"
          name: "FMTLVL"
          desc: "Current fill level of FMT fifo"
        }
        { bits: "21:16"
          name: "RXLVL"
          desc: "Current fill level of RX fifo"
        }
        { bits: "13:8"
          name: "TXLVL"
          desc: "Current fill level of TX fifo"
        }
        { bits: "29:24"
          name: "ACQLVL"
          desc: "Current fill level of ACQ fifo"
        }
      ]
      tags: [// Updated by the hw. Exclude from write-checks.
             "excl:CsrNonInitTests:CsrExclWriteCheck"]
    }
    { name: "OVRD"
      desc: "I2C override control register"
      swaccess: "rw"
      hwaccess: "hro"
      fields: [
        { bits: "0",
          name: "TXOVRDEN",
          desc: "Override the SDA and SCL TX signals."
        }
        { bits: "1",
          name: "SCLVAL",
          desc: "Value for SCL Override. Set to 0 to drive TX Low, and set to 1 for high-Z"
        }
        { bits: "2",
          name: "SDAVAL",
          desc: "Value for SDA Override. Set to 0 to drive TX Low, and set to 1 for high-Z"
        }
      ]
    }
    { name: "VAL"
      desc: "Oversampled RX values"
      swaccess: "ro"
      hwaccess: "hwo"
      hwext:    "true"
      fields: [
        { bits: "15:0"
          name: "SCL_RX"
          desc: '''
                Last 16 oversampled values of SCL. Most recent bit is bit 0, oldest 15.
                '''
        }
        { bits: "31:16"
          name: "SDA_RX"
          desc: '''
                Last 16 oversampled values of SDA. Most recent bit is bit 16, oldest 31.
                '''
        }
      ]
      tags: [// Affected by IO pins - exclude from init and write checks.
             "excl:CsrAllTests:CsrExclCheck"]
    }

    { name: "TIMING0"
      desc: '''
            Detailed I2C Timings (directly corresponding to table 10 in the I2C Specification).
            All values are expressed in units of the input clock period.
            '''
      swaccess: "rw"
      hwaccess: "hro"
      fields: [
        { bits: "15:0"
          name: "THIGH"
          desc: "The actual time to hold SCL high in a given pulse"
        }
        { bits: "31:16"
          name: "TLOW"
          desc: "The actual time to hold SCL low between any two SCL pulses"
        }
      ]
    }
    { name: "TIMING1",
      desc: '''
            Detailed I2C Timings (directly corresponding to table 10 in the I2C Specification).
            All values are expressed in units of the input clock period.
            '''
      swaccess: "rw"
      hwaccess: "hro"
      fields: [
        { bits: "15:0"
          name: "T_R"
          desc: "The nominal rise time to anticipate for the bus (depends on capacitance)"
        }
        { bits: "31:16"
          name: "T_F"
          desc: "The nominal fall time to anticipate for the bus (influences SDA hold times)"
        }
      ]
    }
    { name: "TIMING2"
      desc: '''
            Detailed I2C Timings (directly corresponding to table 10 in the I2C Specification).
            All values are expressed in units of the input clock period.
            '''
      swaccess: "rw"
      hwaccess: "hro"
      fields: [
        { bits: "15:0"
          name: "TSU_STA"
          desc: "Actual setup time for repeated start signals"
        }
        { bits: "31:16"
          name: "THD_STA"
          desc: "Actual hold time for start signals"
        }
      ]
    }
    { name: "TIMING3"
      desc: '''
            Detailed I2C Timings (directly corresponding to table 10, in the I2C Specification).
            All values are expressed in units of the input clock period.
            '''
      swaccess: "rw"
      hwaccess: "hro"
      fields: [
        { bits: "15:0"
          name: "TSU_DAT"
          desc: "Actual setup time for data (or ack) bits"
        }
        { bits: "31:16"
          name: "THD_DAT"
          desc: '''
                Actual hold time for data (or ack) bits
                (Note, where required, the parameters TVD_DAT is taken to be THD_DAT+T_F)
                '''
        }
      ]
    }
    { name: "TIMING4"
      desc: '''
            Detailed I2C Timings (directly corresponding to table 10, in the I2C Specification).
            All values are expressed in units of the input clock period.
            '''
      swaccess: "rw"
      hwaccess: "hro"
      fields: [
        { bits: "15:0"
          name: "TSU_STO"
          desc: "Actual setup time for stop signals"
        }
        { bits: "31:16"
          name: "T_BUF"
          desc: "Actual time between each STOP signal and the following START signal"
        }
      ]
    }
    { name: "TIMEOUT_CTRL"
      desc: "I2C clock stretching timeout control"
      swaccess: "rw"
      hwaccess: "hro"
      fields: [
        { bits: "30:0"
          name: "VAL"
          desc: "Clock stretching timeout value (in units of input clock frequency)"
        }
        { bits: "31"
          name: "EN"
          desc: "Enable timeout feature"
        }
      ]
    }
    { name: "TARGET_ID"
      desc: "I2C target address and mask pairs"
      swaccess: "rw"
      hwaccess: "hro"
      fields: [
        { bits: "6:0"
          name: "ADDRESS0"
          desc: "I2C target address number 0"
        }
        { bits: "13:7"
          name: "MASK0"
          desc: "I2C target mask number 0"
        }
        { bits: "20:14"
          name: "ADDRESS1"
          desc: "I2C target address number 1"
        }
        { bits: "27:21"
          name: "MASK1"
          desc: "I2C target mask number 1"
        }
      ]
    }
    { name: "ACQDATA"
      desc: "I2C target acquired data"
      swaccess: "ro"
      hwaccess: "hrw"
      hwext: "true"
      hwre: "true"
      fields: [
        { bits: "7:0"
          name: "ABYTE"
          desc: "Address for accepted transaction or acquired byte"
        }
        { bits: "9:8"
          name: "SIGNAL"
          desc: "Host issued a START before transmitting ABYTE, a STOP or a RESTART after the preceeding ABYTE"
        }
      ]
      tags: [// Updated by the hw. Exclude from init and write-checks.
             // Without actual I2C traffic, read from this FIFO returns Xs.
             "excl:CsrAllTests:CsrExclCheck"]
    }
    { name: "TXDATA"
      desc: "I2C target transmit data"
      swaccess: "wo"
      hwaccess: "hro"
      hwqe: "true"
      fields: [
        { bits: "7:0" }
      ]
    }
    { name: "STRETCH_CTRL"
      desc: "I2C target clock stretching control"
      swaccess: "rw"
      fields: [
        { bits: "0"
          hwaccess: "hro"
          name: "EN_ADDR_TX"
          desc: "Enable clock stretching after address matching completes for transmit (read)"
        }
        { bits: "1"
          hwaccess: "hro"
          name: "EN_ADDR_ACQ"
          desc: "Enable clock stretching after address matching completes for acquire (write)"
        }
        { bits: "2"
          hwaccess: "hrw"
          name: "STOP_TX"
          desc: "Stop clock stretching for transmit (read) and resume normal operation"
        }
        { bits: "3"
          hwaccess: "hrw"
          name: "STOP_ACQ"
          desc: "Stop clock stretching for acquire (write) and resume normal operation"
        }
      ]
    }
    { name: "HOST_TIMEOUT_CTRL"
      desc: "I2C host clock generation timeout value (in units of input clock frequency)"
      swaccess: "rw"
      hwaccess: "hro"
      fields: [
        { bits: "31:0" }
      ]
    }
  ]
}