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",
  human_name:         "I2C Interface",
  one_line_desc:      "I2C interface for host and device mode, supporting up to 1 Mbaud data rates",
  one_paragraph_desc: '''
  I2C Interface implements the I2C serial communication protocol.
  It can be configured in host (master) or device (slave) mode and supports standard data rate (100 kbaud), fast data rate (400 kbaud), and fast plus data rate (1 Mbaud).
  In addition to supporting all mandatory I2C features, this block supports clock stretching in host mode and automatic clock stretching in device mode.
  I2C Interface uses a 7-bit address space and is compatible with any device covered by I2C specification operating at speeds up to 1 Mbaud.
  '''
  design_spec:        "../doc",
  dv_doc:             "../doc/dv",
  hw_checklist:       "../doc/checklist",
  sw_checklist:       "/sw/device/lib/dif/dif_i2c",
  revisions: [
    {
      version:            "1.0",
      life_stage:         "L1",
      design_stage:       "D2S",
      verification_stage: "V1",
      dif_stage:          "S2",
      notes:              ""
    }
  ]
  clocking: [{clock: "clk_i", reset: "rst_ni"}],
  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_threshold"
      desc: "host mode interrupt: raised when the FMT FIFO depth is less than the low threshold."
    }
    { name: "rx_threshold"
      desc: "host mode interrupt: raised if the RX FIFO is greater than the high threshold."
    }
    { name: "fmt_overflow"
      desc: "host mode interrupt: raised if the FMT FIFO has overflowed."
    }
    { name: "rx_overflow"
      desc: "host mode interrupt: raised if the RX FIFO has overflowed."
    }
    { name: "nak"
      desc: "host mode interrupt: raised if there is no ACK in response to an address or data write"
    }
    { name: "scl_interference"
      desc: "host mode interrupt: raised if the SCL line drops early (not supported without clock synchronization)."
    }
    { name: "sda_interference"
      desc: "host mode interrupt: raised if the SDA line goes low when host is trying to assert high"
    }
    { name: "stretch_timeout"
      desc: "host mode interrupt: raised if target stretches the clock beyond the allowed timeout period"
    }
    { name: "sda_unstable"
      desc: "host mode interrupt: raised if the target does not assert a constant value of SDA during transmission."
    }
    { name: "cmd_complete"
      desc: '''
        host and target mode interrupt.
        In host mode, raised if the host issues a repated START or terminates the transaction by issuing STOP.
        In target mode, raised if the external host issues a STOP or repeated START.
      '''
    }
    { name: "tx_stretch"
      desc: "target mode interrupt: raised if the target is stretching clocks for a read command.  This is a level status interrupt."
      type: "status"
    }
    { name: "tx_overflow"
      desc: "target mode interrupt: raised if TX FIFO has overflowed."
    }
    { name: "acq_full"
      desc: "target mode interrupt: raised if ACQ FIFO becomes full.  This is a level status interrupt."
      type: "status"
    }
    { name: "unexp_stop"
      desc: "target mode interrupt: raised if STOP is received without a preceding NACK during an external host read."
    }
    { name: "host_timeout"
      desc: "target mode interrupt: raised if the host stops sending the clock during an ongoing transaction."
    }
  ],
  alert_list: [
    { name: "fatal_fault",
      desc: '''
      This fatal alert is triggered when a fatal TL-UL bus integrity fault is detected.
      '''
    }
  ],
  param_list: [
    { name: "FifoDepth",
      desc: "Depth of FMT, RX, TX, and ACQ FIFOs",
      type: "int",
      default: "64",
    }
  ],
  countermeasures: [
    { name: "BUS.INTEGRITY",
      desc: "End-to-end bus integrity scheme."
    }
  ]

  // 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 FIFO is full"
        }
        { bits: "1"
          name: "RXFULL"
          desc: "RX FIFO 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_threshold 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_threshold 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: "6:0"
          name: "FMTLVL"
          desc: "Current fill level of FMT fifo"
        }
        { bits: "22:16"
          name: "RXLVL"
          desc: "Current fill level of RX fifo"
        }
        { bits: "14:8"
          name: "TXLVL"
          desc: "Current fill level of TX fifo"
        }
        { bits: "30:24"
          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: "HOST_TIMEOUT_CTRL"
      desc: "I2C host clock generation timeout value (in units of input clock frequency)"
      swaccess: "rw"
      hwaccess: "hro"
      fields: [
        { bits: "31:0" }
      ]
    }
  ]
}