| // Copyright lowRISC contributors. |
| // Licensed under the Apache License, Version 2.0, see LICENSE for details. |
| // SPDX-License-Identifier: Apache-2.0 |
| // |
| // Description: I2C finite state machine |
| |
| module i2c_fsm ( |
| input clk_i, // clock |
| input rst_ni, // active low reset |
| |
| input scl_i, // serial clock input from i2c bus |
| output scl_o, // serial clock output to i2c bus |
| input sda_i, // serial data input from i2c bus |
| output sda_o, // serial data output to i2c bus |
| |
| input host_enable_i, // enable host functionality |
| input target_enable_i, // enable target functionality |
| |
| input fmt_fifo_rvalid_i, // indicates there is valid data in fmt_fifo |
| input fmt_fifo_wvalid_i, // indicates data is being put into fmt_fifo |
| input [5:0] fmt_fifo_depth_i, // fmt_fifo_depth |
| output logic fmt_fifo_rready_o, // populates fmt_fifo |
| input [7:0] fmt_byte_i, // byte in fmt_fifo to be sent to target |
| input fmt_flag_start_before_i, // issue start before sending byte |
| input fmt_flag_stop_after_i, // issue stop after sending byte |
| input fmt_flag_read_bytes_i, // indicates byte is an number of reads |
| input fmt_flag_read_continue_i,// host to send Ack to final byte read |
| input fmt_flag_nak_ok_i, // no Ack is expected |
| |
| output logic rx_fifo_wvalid_o, // high if there is valid data in rx_fifo |
| output logic [7:0] rx_fifo_wdata_o, // byte in rx_fifo read from target |
| |
| input tx_fifo_rvalid_i, // indicates there is valid data in tx_fifo |
| input tx_fifo_wvalid_i, // indicates data is being put into tx_fifo |
| input [5:0] tx_fifo_depth_i, // tx_fifo_depth |
| output logic tx_fifo_rready_o, // populates tx_fifo |
| input [7:0] tx_fifo_rdata_i, // byte in tx_fifo to be sent to host |
| |
| output logic acq_fifo_wvalid_o, // high if there is valid data in acq_fifo |
| output logic [9:0] acq_fifo_wdata_o, // byte and signal in acq_fifo read from target |
| |
| output logic host_idle_o, // indicates the host is idle |
| output logic target_idle_o, // indicates the target is idle |
| |
| input [15:0] thigh_i, // high period of the SCL in clock units |
| input [15:0] tlow_i, // low period of the SCL in clock units |
| input [15:0] t_r_i, // rise time of both SDA and SCL in clock units |
| input [15:0] t_f_i, // fall time of both SDA and SCL in clock units |
| input [15:0] thd_sta_i, // hold time for (repeated) START in clock units |
| input [15:0] tsu_sta_i, // setup time for repeated START in clock units |
| input [15:0] tsu_sto_i, // setup time for STOP in clock units |
| input [15:0] tsu_dat_i, // data setup time in clock units |
| input [15:0] thd_dat_i, // data hold time in clock units |
| input [15:0] t_buf_i, // bus free time between STOP and START in clock units |
| input [30:0] stretch_timeout_i, // max time target may stretch the clock |
| input timeout_enable_i, // assert if target stretches clock past max |
| |
| input logic [6:0] target_address0_i, |
| input logic [6:0] target_mask0_i, |
| input logic [6:0] target_address1_i, |
| input logic [6:0] target_mask1_i, |
| |
| output logic event_nak_o, // target didn't Ack when expected |
| output logic event_scl_interference_o, // other device forcing SCL low |
| output logic event_sda_interference_o, // other device forcing SDA low |
| output logic event_stretch_timeout_o, // target stretches clock past max time |
| output logic event_sda_unstable_o, // SDA is not constant during SCL pulse |
| output logic event_trans_complete_o, // Transaction is complete |
| output logic event_tx_empty_o, // tx_fifo is empty but data is needed |
| output logic event_tx_nonempty_o, // tx_fifo is nonempty after stop |
| output logic event_ack_stop_o // target received stop after ack |
| ); |
| |
| // I2C bus clock timing variables |
| logic [19:0] tcount_q; // current counter for setting delays |
| logic [19:0] tcount_d; // next counter for setting delays |
| logic load_tcount; // indicates counter must be loaded |
| logic [30:0] stretch; // counter for clock being stretched by target |
| |
| // Bit and byte counter variables |
| logic [2:0] bit_index; // bit being transmitted to or read from the bus |
| logic bit_decr; // indicates bit_index must be decremented by 1 |
| logic bit_clr; // indicates bit_index must be reset to 7 |
| logic [8:0] byte_num; // number of bytes to read |
| logic [8:0] byte_index; // byte being read from the bus |
| logic byte_decr; // indicates byte_index must be decremented by 1 |
| logic byte_clr; // indicates byte_index must be reset to byte_num |
| |
| // Other internal variables |
| logic scl_temp; // scl internal |
| logic sda_temp; // data internal |
| logic scl_i_q; // scl_i delayed by one clock |
| logic sda_i_q; // sda_i delayed by one clock |
| logic [7:0] read_byte; // register for reads from target |
| logic read_byte_clr; // clear read_byte contents |
| logic shift_data_en; // indicates data must be shifted in from the bus |
| logic no_stop; // indicates no stop has been issued before start |
| logic log_start; // indicates start is been issued |
| logic log_stop; // indicates stop is been issued |
| logic restart; // indicates repeated start state is entered into |
| |
| // Target specific variables |
| logic start_det; // indicates start or repeated start is detected on the bus |
| logic stop_det; // indicates stop is detected on the bus |
| logic address0_match;// indicates target's address0 matches the one sent by host |
| logic address1_match;// indicates target's address1 matches the one sent by host |
| logic address_match; // indicates one of target's addresses matches the one sent by host |
| logic [7:0] input_byte; // register for reads from host |
| logic input_byte_clr;// clear input_byte contents |
| |
| // Target bit counter variables |
| logic [3:0] bit_idx; // bit index including ack/nack |
| logic bit_ack; // indicates ACK bit been sent or received |
| logic rw_bit; // indicates host wants to read (1) or write (0) |
| logic host_ack; // indicates host acqnowledged transmitted byte |
| |
| // Clock counter implementation |
| typedef enum logic [3:0] { |
| tSetupStart, tHoldStart, tClockLow, tSetupBit, tClockPulse, tHoldBit, |
| tClockStart, tClockStop, tSetupStop, tHoldStop, tNoDelay |
| } tcount_sel_e; |
| |
| tcount_sel_e tcount_sel; |
| |
| always_comb begin : counter_functions |
| tcount_d = tcount_q; |
| if (load_tcount) begin |
| unique case (tcount_sel) |
| tSetupStart : tcount_d = 20'(t_r_i) + 20'(tsu_sta_i); |
| tHoldStart : tcount_d = 20'(t_f_i) + 20'(thd_sta_i); |
| tClockStart : tcount_d = 20'(thd_dat_i); |
| tClockLow : tcount_d = 20'(tlow_i) - 20'(t_r_i) - 20'(tsu_dat_i) - 20'(thd_dat_i); |
| tSetupBit : tcount_d = 20'(t_r_i) + 20'(tsu_dat_i); |
| tClockPulse : tcount_d = 20'(t_r_i) + 20'(thigh_i) + 20'(t_f_i); |
| tHoldBit : tcount_d = 20'(t_f_i) + 20'(thd_dat_i); |
| tClockStop : tcount_d = 20'(t_f_i) + 20'(tlow_i) - 20'(thd_dat_i); |
| tSetupStop : tcount_d = 20'(t_r_i) + 20'(tsu_sto_i); |
| tHoldStop : tcount_d = 20'(t_r_i) + 20'(t_buf_i) - 20'(tsu_sta_i); |
| tNoDelay : tcount_d = 20'h00001; |
| default : tcount_d = 20'h00001; |
| endcase |
| end else if (stretch == '0) begin |
| tcount_d = tcount_q - 1'b1; |
| end else begin |
| tcount_d = tcount_q; // pause timer if clock is stretched |
| end |
| end |
| |
| always_ff @ (posedge clk_i or negedge rst_ni) begin : clk_counter |
| if (!rst_ni) begin |
| tcount_q <= '1; |
| end else begin |
| tcount_q <= tcount_d; |
| end |
| end |
| |
| // Clock stretching detection |
| always_ff @ (posedge clk_i or negedge rst_ni) begin : clk_stretch |
| if (!rst_ni) begin |
| stretch <= '0; |
| end else if (scl_temp == 1'b1 && scl_i == '0) begin |
| stretch <= stretch + 1'b1; |
| end else begin |
| stretch <= '0; |
| end |
| end |
| |
| // Bit index implementation |
| always_ff @ (posedge clk_i or negedge rst_ni) begin : bit_counter |
| if (!rst_ni) begin |
| bit_index <= 3'd7; |
| end else if (bit_clr) begin |
| bit_index <= 3'd7; |
| end else if (bit_decr) begin |
| bit_index <= bit_index - 1'b1; |
| end else begin |
| bit_index <= bit_index; |
| end |
| end |
| |
| // Deserializer for a byte read from the bus |
| always_ff @ (posedge clk_i or negedge rst_ni) begin : read_register |
| if (!rst_ni) begin |
| read_byte <= 8'h00; |
| end else if (read_byte_clr) begin |
| read_byte <= 8'h00; |
| end else if (shift_data_en) begin |
| read_byte[7:0] <= {read_byte[6:0], sda_i}; // MSB goes in first |
| end |
| end |
| |
| // Number of bytes to read |
| always_comb begin : byte_number |
| if (!fmt_flag_read_bytes_i) byte_num = 9'd0; |
| else if (fmt_byte_i == '0) byte_num = 9'd256; |
| else byte_num = 9'(fmt_byte_i); |
| end |
| |
| // Byte index implementation |
| always_ff @ (posedge clk_i or negedge rst_ni) begin : byte_counter |
| if (!rst_ni) begin |
| byte_index <= '0; |
| end else if (byte_clr) begin |
| byte_index <= byte_num; |
| end else if (byte_decr) begin |
| byte_index <= byte_index - 1'b1; |
| end else begin |
| byte_index <= byte_index; |
| end |
| end |
| |
| // SDA and SCL at the previous clock edge |
| always_ff @ (posedge clk_i or negedge rst_ni) begin : bus_prev |
| if (!rst_ni) begin |
| scl_i_q <= 1'b1; |
| sda_i_q <= 1'b1; |
| end else begin |
| scl_i_q <= scl_i; |
| sda_i_q <= sda_i; |
| end |
| end |
| |
| // Stop issued before |
| always_ff @ (posedge clk_i or negedge rst_ni) begin : stop_state |
| if (!rst_ni) begin |
| no_stop <= 1'b0; |
| end else if (log_stop) begin |
| no_stop <= 1'b0; |
| end else if (log_start) begin |
| no_stop <= 1'b1; |
| end else begin |
| no_stop <= no_stop; |
| end |
| end |
| |
| // (Repeated) Start condition detection by target |
| always_ff @ (posedge clk_i or negedge rst_ni) begin : s_detect |
| if (!rst_ni) begin |
| start_det <= 1'b0; |
| end else if (scl_i_q == 1'b1 && scl_i == 1'b1) begin |
| if (sda_i_q == 1'b1 && sda_i == '0) start_det <= 1'b1; |
| else start_det <= 1'b0; |
| end else begin |
| start_det <= 1'b0; |
| end |
| end |
| |
| // Stop condition detection by target |
| always_ff @ (posedge clk_i or negedge rst_ni) begin : p_detect |
| if (!rst_ni) begin |
| stop_det <= 1'b0; |
| end else if (scl_i_q == 1'b1 && scl_i == 1'b1) begin |
| if (sda_i_q == '0 && sda_i == 1'b1) stop_det <= 1'b1; |
| else stop_det <= 1'b0; |
| end else begin |
| stop_det <= 1'b0; |
| end |
| end |
| |
| // Bit counter on the target side |
| assign bit_ack = (bit_idx == 4'd8) && !start_det; // ack |
| |
| // Increment counter on negative SCL edge |
| always_ff @ (posedge clk_i or negedge rst_ni) begin : tgt_bit_counter |
| if (!rst_ni) begin |
| bit_idx <= 4'd0; |
| end else if (start_det || bit_ack) begin |
| bit_idx <= 4'd0; |
| end else if (scl_i_q == 1'b1 && scl_i == '0) begin |
| bit_idx <= bit_idx + 1'b1; |
| end else begin |
| bit_idx <= bit_idx; |
| end |
| end |
| |
| // Deserializer for a byte read from the bus on the target side |
| assign address0_match = ((input_byte[7:1] & target_mask0_i) == target_address0_i); |
| assign address1_match = ((input_byte[7:1] & target_mask1_i) == target_address1_i); |
| assign address_match = (address0_match || address1_match); |
| assign rw_bit = input_byte[0]; |
| |
| // Shift data in on positive SCL edge |
| always_ff @ (posedge clk_i or negedge rst_ni) begin : tgt_input_register |
| if (!rst_ni) begin |
| input_byte <= 8'h00; |
| end else if (input_byte_clr) begin |
| input_byte <= 8'h00; |
| end else if (scl_i_q == '0 && scl_i == 1'b1) begin |
| if (!bit_ack) input_byte[7:0] <= {input_byte[6:0], sda_i}; // MSB goes in first |
| end |
| end |
| |
| // Detection by the target of ACK bit send by the host |
| always_ff @ (posedge clk_i or negedge rst_ni) begin : host_ack_register |
| if (!rst_ni) begin |
| host_ack <= 1'b0; |
| end else if (scl_i_q == '0 && scl_i == 1'b1) begin |
| if (bit_ack) host_ack <= ~sda_i; |
| end |
| end |
| |
| // State definitions |
| typedef enum logic [5:0] { |
| Idle, PopFmtFifo, SetupStart, HoldStart, SetupStop, HoldStop, |
| ClockLow, SetupBit, ClockPulse, HoldBit, |
| ClockLowAck, SetupDevAck, ClockPulseAck, HoldDevAck, |
| ReadClockLow, ReadSetupBit, ReadClockPulse, ReadHoldBit, |
| HostClockLowAck, HostSetupBitAck, HostClockPulseAck, HostHoldBitAck, |
| Active, ClockStart, ClockStop, |
| AddrRead, AddrAckWait, AddrAckSetup, AddrAckPulse, AddrAckHold, |
| TransmitWait, TransmitSetup, TransmitPulse, TransmitHold, TransmitAck, |
| AcquireByte, AcquireAckWait, AcquireAckSetup, AcquireAckPulse, AcquireAckHold, |
| PopTxFifo, StretchClock, AcquireSrP |
| } state_e; |
| |
| state_e state_q, state_d; |
| |
| // Outputs for each state |
| always_comb begin : state_outputs |
| host_idle_o = 1'b1; |
| target_idle_o = 1'b1; |
| sda_temp = 1'b1; |
| scl_temp = 1'b1; |
| fmt_fifo_rready_o = 1'b0; |
| rx_fifo_wvalid_o = 1'b0; |
| rx_fifo_wdata_o = 8'h00; |
| tx_fifo_rready_o = 1'b0; |
| acq_fifo_wvalid_o = 1'b0; |
| acq_fifo_wdata_o = 10'b0; |
| event_nak_o = 1'b0; |
| event_scl_interference_o = 1'b0; |
| event_sda_interference_o = 1'b0; |
| event_sda_unstable_o = 1'b0; |
| event_stretch_timeout_o = 1'b0; |
| event_trans_complete_o = 1'b0; |
| event_tx_empty_o = 1'b0; |
| event_tx_nonempty_o = 1'b0; |
| event_ack_stop_o = 1'b0; |
| unique case (state_q) |
| // Idle: initial state, SDA and SCL are released (high) |
| Idle : begin |
| host_idle_o = 1'b1; |
| sda_temp = 1'b1; |
| scl_temp = 1'b1; |
| if (host_enable_i && sda_i == '0) event_sda_interference_o = 1'b1; |
| if (!target_address0_i && !target_mask0_i && !target_address1_i && !target_mask1_i) begin |
| acq_fifo_wvalid_o = 1'b0; |
| end |
| end |
| // SetupStart: SDA and SCL are released |
| SetupStart : begin |
| host_idle_o = 1'b0; |
| sda_temp = 1'b1; |
| scl_temp = 1'b1; |
| if (sda_i == '0) event_sda_interference_o = 1'b1; |
| if (restart == 1'b1) event_trans_complete_o = 1'b1; |
| end |
| // HoldStart: SDA is pulled low, SCL is released |
| HoldStart : begin |
| host_idle_o = 1'b0; |
| sda_temp = 1'b0; |
| scl_temp = 1'b1; |
| end |
| // ClockStart: SCL is pulled low, SDA stays low |
| ClockStart : begin |
| host_idle_o = 1'b0; |
| sda_temp = 1'b0; |
| scl_temp = 1'b0; |
| end |
| // ClockLow: SCL is pulled low, SDA stays low |
| ClockLow : begin |
| host_idle_o = 1'b0; |
| sda_temp = 1'b0; |
| scl_temp = 1'b0; |
| end |
| // SetupBit: Shift indexed bit onto SDA, SCL stays low |
| SetupBit : begin |
| host_idle_o = 1'b0; |
| sda_temp = fmt_byte_i[bit_index]; |
| scl_temp = 1'b0; |
| if (sda_temp == 1'b1 && sda_i == '0) event_sda_interference_o = 1'b1; |
| end |
| // ClockPulse: SCL is released, SDA keeps the indexed bit value |
| ClockPulse : begin |
| host_idle_o = 1'b0; |
| sda_temp = fmt_byte_i[bit_index]; |
| scl_temp = 1'b1; |
| if ((stretch > stretch_timeout_i) && timeout_enable_i) begin |
| event_stretch_timeout_o = 1'b1; |
| end |
| if (scl_i_q == 1'b1 && scl_i == '0) event_scl_interference_o = 1'b1; |
| if (sda_temp == 1'b1 && sda_i == '0) event_sda_interference_o = 1'b1; |
| if (sda_i_q != sda_i) event_sda_unstable_o = 1'b1; |
| end |
| // HoldBit: SCL is pulled low |
| HoldBit : begin |
| host_idle_o = 1'b0; |
| sda_temp = fmt_byte_i[bit_index]; |
| scl_temp = 1'b0; |
| if (sda_temp == 1'b1 && sda_i == '0) event_sda_interference_o = 1'b1; |
| end |
| // ClockLowAck: SCL and SDA are pulled low |
| ClockLowAck : begin |
| host_idle_o = 1'b0; |
| sda_temp = 1'b0; |
| scl_temp = 1'b0; |
| end |
| // SetupDevAck: SDA is released, waiting for target to pull it low |
| SetupDevAck : begin |
| host_idle_o = 1'b0; |
| sda_temp = 1'b1; |
| scl_temp = 1'b0; |
| end |
| // ClockPulseAck: SCL is released |
| ClockPulseAck : begin |
| host_idle_o = 1'b0; |
| sda_temp = 1'b1; |
| scl_temp = 1'b1; |
| if (sda_i == '0 && !fmt_flag_nak_ok_i) event_nak_o = 1'b1; |
| if ((stretch > stretch_timeout_i) && timeout_enable_i) begin |
| event_stretch_timeout_o = 1'b1; |
| end |
| if (scl_i_q == 1'b1 && scl_i == '0) event_scl_interference_o = 1'b1; |
| if (sda_i_q != sda_i) event_sda_unstable_o = 1'b1; |
| end |
| // HoldDevAck: SCL is pulled low |
| HoldDevAck : begin |
| host_idle_o = 1'b0; |
| sda_temp = 1'b1; |
| scl_temp = 1'b0; |
| end |
| // ReadClockLow: SCL is pulled low, SDA is released |
| ReadClockLow : begin |
| host_idle_o = 1'b0; |
| sda_temp = 1'b1; |
| scl_temp = 1'b0; |
| end |
| // ReadSetupBit: Read indexed bit off SDA, SCL stays low |
| ReadSetupBit : begin |
| host_idle_o = 1'b0; |
| scl_temp = 1'b0; |
| end |
| // ReadClockPulse: SCL is released, the indexed bit value is read off SDA |
| ReadClockPulse : begin |
| host_idle_o = 1'b0; |
| scl_temp = 1'b1; |
| if ((stretch > stretch_timeout_i) && timeout_enable_i) begin |
| event_stretch_timeout_o = 1'b1; |
| end |
| if (scl_i_q == 1'b1 && scl_i == '0) event_scl_interference_o = 1'b1; |
| if (sda_i_q != sda_i) event_sda_unstable_o = 1'b1; |
| end |
| // ReadHoldBit: SCL is pulled low |
| ReadHoldBit : begin |
| host_idle_o = 1'b0; |
| scl_temp = 1'b0; |
| if (bit_index == '0 && tcount_q == 20'd1) begin |
| rx_fifo_wdata_o = read_byte; // transfer read data to rx_fifo |
| rx_fifo_wvalid_o = 1'b1; // assert that rx_fifo has valid data |
| end |
| end |
| // HostClockLowAck: SCL and SDA are pulled low |
| HostClockLowAck : begin |
| host_idle_o = 1'b0; |
| sda_temp = 1'b0; |
| scl_temp = 1'b0; |
| end |
| // HostSetupBitAck: Shift Ack/Nack bit onto SDA |
| HostSetupBitAck : begin |
| host_idle_o = 1'b0; |
| if (fmt_flag_read_continue_i) sda_temp = 1'b0; |
| else if (byte_index == 9'd1) sda_temp = 1'b1; |
| else sda_temp = 1'b0; |
| scl_temp = 1'b0; |
| if (sda_temp == 1'b1 && sda_i == '0) event_sda_interference_o = 1'b1; |
| end |
| // HostClockPulseAck: SCL is released |
| HostClockPulseAck : begin |
| host_idle_o = 1'b0; |
| if (fmt_flag_read_continue_i) sda_temp = 1'b0; |
| else if (byte_index == 9'd1) sda_temp = 1'b1; |
| else sda_temp = 1'b0; |
| scl_temp = 1'b1; |
| if ((stretch > stretch_timeout_i) && timeout_enable_i) begin |
| event_stretch_timeout_o = 1'b1; |
| end |
| if (scl_i_q == 1'b1 && scl_i == '0) event_scl_interference_o = 1'b1; |
| if (sda_temp == 1'b1 && sda_i == '0) event_sda_interference_o = 1'b1; |
| if (sda_i_q != sda_i) event_sda_unstable_o = 1'b1; |
| end |
| // HostHoldBitAck: SCL is pulled low |
| HostHoldBitAck : begin |
| host_idle_o = 1'b0; |
| if (fmt_flag_read_continue_i) sda_temp = 1'b0; |
| else if (byte_index == 9'd1) sda_temp = 1'b1; |
| else sda_temp = 1'b0; |
| scl_temp = 1'b0; |
| if (sda_temp == 1'b1 && sda_i == '0) event_sda_interference_o = 1'b1; |
| end |
| // ClockStop: SCL is pulled low, SDA stays low |
| ClockStop : begin |
| host_idle_o = 1'b0; |
| sda_temp = 1'b0; |
| scl_temp = 1'b0; |
| end |
| // SetupStop: SDA is pulled low, SCL is released |
| SetupStop : begin |
| host_idle_o = 1'b0; |
| sda_temp = 1'b0; |
| scl_temp = 1'b1; |
| end |
| // HoldStop: SDA and SCL are released |
| HoldStop : begin |
| host_idle_o = 1'b0; |
| sda_temp = 1'b1; |
| scl_temp = 1'b1; |
| if (sda_i == '0) event_sda_interference_o = 1'b1; |
| event_trans_complete_o = 1'b1; |
| end |
| // Active: continue while keeping SCL low |
| Active : begin |
| host_idle_o = 1'b0; |
| scl_temp = 1'b0; |
| end |
| // PopFmtFifo: populate fmt_fifo |
| PopFmtFifo : begin |
| host_idle_o = 1'b0; |
| if (fmt_flag_stop_after_i) scl_temp = 1'b1; |
| else scl_temp = 1'b0; |
| fmt_fifo_rready_o = 1'b1; |
| end |
| // AddrRead: read and compare target address |
| AddrRead : begin |
| target_idle_o = 1'b0; |
| if (bit_ack && address_match) begin |
| acq_fifo_wdata_o = {1'b0, 1'b1, input_byte}; // transfer data to acq_fifo |
| acq_fifo_wvalid_o = 1'b1; // assert that acq_fifo has valid data |
| if (tx_fifo_depth_i == '0 && rw_bit) event_tx_empty_o = 1'b1; |
| end |
| end |
| // AddrAckWait: pause before acknowledging |
| AddrAckWait : begin |
| target_idle_o = 1'b0; |
| end |
| // AddrAckSetup: target pulls SDA low while SCL is low |
| AddrAckSetup : begin |
| target_idle_o = 1'b0; |
| sda_temp = 1'b0; |
| end |
| // AddrAckPulse: target pulls SDA low while SCL is released |
| AddrAckPulse : begin |
| target_idle_o = 1'b0; |
| sda_temp = 1'b0; |
| end |
| // AddrAckHold: target pulls SDA low while SCL is pulled low |
| AddrAckHold : begin |
| target_idle_o = 1'b0; |
| sda_temp = 1'b0; |
| end |
| // TransmitWait: pause before sending a bit |
| TransmitWait : begin |
| target_idle_o = 1'b0; |
| end |
| // TransmitSetup: target shifts indexed bit onto SDA while SCL is low |
| TransmitSetup : begin |
| target_idle_o = 1'b0; |
| sda_temp = tx_fifo_rdata_i[3'(bit_idx)]; |
| end |
| // TransmitPulse: target shifts indexed bit onto SDA while SCL is released |
| TransmitPulse : begin |
| target_idle_o = 1'b0; |
| sda_temp = tx_fifo_rdata_i[3'(bit_idx)]; |
| end |
| // TransmitHold: target shifts indexed bit onto SDA while SCL is pulled low |
| TransmitHold : begin |
| target_idle_o = 1'b0; |
| sda_temp = tx_fifo_rdata_i[3'(bit_idx)]; |
| end |
| // TransmitAck: target waits for host to ACK transmission |
| TransmitAck : begin |
| target_idle_o = 1'b0; |
| if (tx_fifo_depth_i == 6'd1 && !tx_fifo_wvalid_i && host_ack) event_tx_empty_o = 1'b1; |
| if (host_ack && (start_det || stop_det)) event_ack_stop_o = 1'b1; |
| end |
| // PopTxFifo: populate tx_fifo |
| PopTxFifo : begin |
| target_idle_o = 1'b0; |
| tx_fifo_rready_o = 1'b1; |
| end |
| // StretchClock: target stretches the clock |
| StretchClock : begin |
| target_idle_o = 1'b0; |
| tx_fifo_rready_o = 1'b1; |
| scl_temp = 1'b0; |
| if (tx_fifo_depth_i == '0) event_tx_empty_o = 1'b1; |
| end |
| // AcquireByte: target acquires a byte |
| AcquireByte : begin |
| target_idle_o = 1'b0; |
| if (bit_ack) begin |
| acq_fifo_wdata_o = {1'b0, 1'b0, input_byte}; // transfer data to acq_fifo |
| acq_fifo_wvalid_o = 1'b1; // assert that acq_fifo has valid data |
| end |
| end |
| // AcquireAckWait: pause before acknowledging |
| AcquireAckWait : begin |
| target_idle_o = 1'b0; |
| end |
| // AcquireAckSetup: target pulls SDA low while SCL is low |
| AcquireAckSetup : begin |
| target_idle_o = 1'b0; |
| sda_temp = 1'b0; |
| end |
| // AcquireAckPulse: target pulls SDA low while SCL is released |
| AcquireAckPulse : begin |
| target_idle_o = 1'b0; |
| sda_temp = 1'b0; |
| end |
| // AcquireAckHold: target pulls SDA low while SCL is pulled low |
| AcquireAckHold : begin |
| target_idle_o = 1'b0; |
| sda_temp = 1'b0; |
| end |
| // AcquireSrP: target acquires repeated Start or Stop |
| AcquireSrP : begin |
| if (start_det) acq_fifo_wdata_o = {1'b1, 1'b1, input_byte}; |
| else acq_fifo_wdata_o = {1'b1, 1'b0, input_byte}; |
| acq_fifo_wvalid_o = 1'b1; |
| if (tx_fifo_depth_i != '0) event_tx_nonempty_o = 1'b1; |
| end |
| // default |
| default : begin |
| host_idle_o = 1'b1; |
| target_idle_o = 1'b1; |
| sda_temp = 1'b1; |
| scl_temp = 1'b1; |
| fmt_fifo_rready_o = 1'b0; |
| rx_fifo_wvalid_o = 1'b0; |
| rx_fifo_wdata_o = 8'h00; |
| tx_fifo_rready_o = 1'b0; |
| acq_fifo_wvalid_o = 1'b0; |
| acq_fifo_wdata_o = 10'b0; |
| event_nak_o = 1'b0; |
| event_scl_interference_o = 1'b0; |
| event_sda_interference_o = 1'b0; |
| event_sda_unstable_o = 1'b0; |
| event_stretch_timeout_o = 1'b0; |
| event_trans_complete_o = 1'b0; |
| event_tx_empty_o = 1'b0; |
| event_tx_nonempty_o = 1'b0; |
| event_ack_stop_o = 1'b0; |
| end |
| endcase |
| end |
| |
| // Conditional state transition |
| always_comb begin : state_functions |
| state_d = state_q; |
| load_tcount = 1'b0; |
| tcount_sel = tNoDelay; |
| bit_decr = 1'b0; |
| bit_clr = 1'b0; |
| byte_decr = 1'b0; |
| byte_clr = 1'b0; |
| read_byte_clr = 1'b0; |
| shift_data_en = 1'b0; |
| log_start = 1'b0; |
| log_stop = 1'b0; |
| restart = 1'b0; |
| input_byte_clr = 1'b0; |
| |
| unique case (state_q) |
| // Idle: initial state, SDA and SCL are released (high) |
| Idle : begin |
| if (!host_enable_i && !target_enable_i) state_d = Idle; // Idle unless host is enabled |
| else if (host_enable_i) begin |
| if (!fmt_fifo_rvalid_i) state_d = Idle; |
| else state_d = Active; |
| end else if (target_enable_i) begin |
| if (!start_det) state_d = Idle; |
| else begin |
| state_d = AddrRead; |
| input_byte_clr = 1'b1; |
| end |
| end |
| end |
| |
| // SetupStart: SDA and SCL are released |
| SetupStart : begin |
| if (no_stop) restart = 1'b1; |
| if (tcount_q == 20'd1) begin |
| state_d = HoldStart; |
| load_tcount = 1'b1; |
| tcount_sel = tHoldStart; |
| log_start = 1'b1; |
| end |
| end |
| // HoldStart: SDA is pulled low, SCL is released |
| HoldStart : begin |
| if (tcount_q == 20'd1) begin |
| state_d = ClockStart; |
| load_tcount = 1'b1; |
| tcount_sel = tClockStart; |
| end |
| end |
| // ClockStart: SCL is pulled low, SDA stays low |
| ClockStart : begin |
| if (tcount_q == 20'd1) begin |
| state_d = ClockLow; |
| load_tcount = 1'b1; |
| tcount_sel = tClockLow; |
| end |
| end |
| |
| // ClockLow: SCL is pulled low, SDA stays low |
| ClockLow : begin |
| if (tcount_q == 20'd1) begin |
| state_d = SetupBit; |
| load_tcount = 1'b1; |
| tcount_sel = tSetupBit; |
| end |
| end |
| // SetupBit: Shift indexed bit onto SDA, SCL stays low |
| SetupBit : begin |
| if (tcount_q == 20'd1) begin |
| state_d = ClockPulse; |
| load_tcount = 1'b1; |
| tcount_sel = tClockPulse; |
| end |
| end |
| // ClockPulse: SCL is released, SDA keeps the indexed bit value |
| ClockPulse : begin |
| if (tcount_q == 20'd1) begin |
| state_d = HoldBit; |
| load_tcount = 1'b1; |
| tcount_sel = tHoldBit; |
| end |
| end |
| // HoldBit: SCL is pulled low |
| HoldBit : begin |
| if (tcount_q == 20'd1) begin |
| load_tcount = 1'b1; |
| tcount_sel = tClockLow; |
| if (bit_index == '0) begin |
| state_d = ClockLowAck; |
| bit_clr = 1'b1; |
| end else begin |
| state_d = ClockLow; |
| bit_decr = 1'b1; |
| end |
| end |
| end |
| |
| // ClockLowAck: SCL and SDA are pulled low |
| ClockLowAck : begin |
| if (tcount_q == 20'd1) begin |
| state_d = SetupDevAck; |
| load_tcount = 1'b1; |
| tcount_sel = tSetupBit; |
| end |
| end |
| // SetupDevAck: SDA is released, waiting for target to pull it low |
| SetupDevAck : begin |
| if (tcount_q == 20'd1) begin |
| state_d = ClockPulseAck; |
| load_tcount = 1'b1; |
| tcount_sel = tClockPulse; |
| end |
| end |
| // ClockPulseAck: SCL is released |
| ClockPulseAck : begin |
| if (tcount_q == 20'd1) begin |
| state_d = HoldDevAck; |
| load_tcount = 1'b1; |
| tcount_sel = tHoldBit; |
| end |
| end |
| // HoldDevAck: SCL is pulled low |
| HoldDevAck : begin |
| if (tcount_q == 20'd1) begin |
| if (fmt_flag_stop_after_i) begin |
| state_d = ClockStop; |
| load_tcount = 1'b1; |
| tcount_sel = tClockStop; |
| end else begin |
| state_d = PopFmtFifo; |
| load_tcount = 1'b1; |
| tcount_sel = tNoDelay; |
| end |
| end |
| end |
| |
| // ReadClockLow: SCL is pulled low, SDA is released |
| ReadClockLow : begin |
| if (tcount_q == 20'd1) begin |
| state_d = ReadSetupBit; |
| load_tcount = 1'b1; |
| tcount_sel = tSetupBit; |
| end |
| end |
| // ReadSetupBit: Shift indexed bit onto SDA, SCL stays low |
| ReadSetupBit : begin |
| if (tcount_q == 20'd1) begin |
| state_d = ReadClockPulse; |
| load_tcount = 1'b1; |
| tcount_sel = tClockPulse; |
| end |
| end |
| // ReadClockPulse: SCL is released, the indexed bit value is read off SDA |
| ReadClockPulse : begin |
| if (tcount_q == 20'd1) begin |
| state_d = ReadHoldBit; |
| load_tcount = 1'b1; |
| tcount_sel = tHoldBit; |
| shift_data_en = 1'b1; |
| end |
| end |
| // ReadHoldBit: SCL is pulled low |
| ReadHoldBit : begin |
| if (tcount_q == 20'd1) begin |
| load_tcount = 1'b1; |
| tcount_sel = tClockLow; |
| if (bit_index == '0) begin |
| state_d = HostClockLowAck; |
| bit_clr = 1'b1; |
| read_byte_clr = 1'b1; |
| end else begin |
| state_d = ReadClockLow; |
| bit_decr = 1'b1; |
| end |
| end |
| end |
| |
| // HostClockLowAck: SCL and SDA are pulled low |
| HostClockLowAck : begin |
| if (tcount_q == 20'd1) begin |
| state_d = HostSetupBitAck; |
| load_tcount = 1'b1; |
| tcount_sel = tSetupBit; |
| end |
| end |
| // HostSetupBitAck: Shift Ack/Nack bit onto SDA |
| HostSetupBitAck : begin |
| if (tcount_q == 20'd1) begin |
| state_d = HostClockPulseAck; |
| load_tcount = 1'b1; |
| tcount_sel = tClockPulse; |
| end |
| end |
| // HostClockPulseAck: SCL is released |
| HostClockPulseAck : begin |
| if (tcount_q == 20'd1) begin |
| state_d = HostHoldBitAck; |
| load_tcount = 1'b1; |
| tcount_sel = tHoldBit; |
| end |
| end |
| // HostHoldBitAck: SCL is pulled low |
| HostHoldBitAck : begin |
| if (tcount_q == 20'd1) begin |
| if (byte_index == 9'd1) begin |
| if (fmt_flag_stop_after_i) begin |
| state_d = ClockStop; |
| load_tcount = 1'b1; |
| tcount_sel = tClockStop; |
| end else begin |
| state_d = PopFmtFifo; |
| load_tcount = 1'b1; |
| tcount_sel = tNoDelay; |
| end |
| end else begin |
| state_d = ReadClockLow; |
| load_tcount = 1'b1; |
| tcount_sel = tClockLow; |
| byte_decr = 1'b1; |
| end |
| end |
| end |
| |
| // ClockStop: SCL is pulled low, SDA stays low |
| ClockStop : begin |
| if (tcount_q == 20'd1) begin |
| state_d = SetupStop; |
| load_tcount = 1'b1; |
| tcount_sel = tSetupStop; |
| end |
| end |
| // SetupStop: SDA is pulled low, SCL is released |
| SetupStop : begin |
| if (tcount_q == 20'd1) begin |
| state_d = HoldStop; |
| load_tcount = 1'b1; |
| tcount_sel = tHoldStop; |
| log_stop = 1'b1; |
| end |
| end |
| // HoldStop: SDA and SCL are released |
| HoldStop : begin |
| if (tcount_q == 20'd1) begin |
| if (!host_enable_i) begin |
| state_d = Idle; |
| load_tcount = 1'b1; |
| tcount_sel = tNoDelay; |
| end else begin |
| state_d = PopFmtFifo; |
| load_tcount = 1'b1; |
| tcount_sel = tNoDelay; |
| end |
| end |
| end |
| |
| // Active: continue while keeping SCL low |
| Active : begin |
| if (fmt_flag_read_bytes_i) begin |
| byte_clr = 1'b1; |
| state_d = ReadClockLow; |
| load_tcount = 1'b1; |
| tcount_sel = tClockLow; |
| end else if (fmt_flag_start_before_i) begin |
| state_d = SetupStart; |
| load_tcount = 1'b1; |
| tcount_sel = tSetupStart; |
| end else begin |
| state_d = ClockLow; |
| load_tcount = 1'b1; |
| tcount_sel = tClockLow; |
| end |
| end |
| |
| // PopFmtFifo: populate fmt_fifo |
| PopFmtFifo : begin |
| if (!host_enable_i) begin |
| state_d = ClockStop; |
| load_tcount = 1'b1; |
| tcount_sel = tClockStop; |
| end else if (fmt_fifo_depth_i == 6'd1 && !fmt_fifo_wvalid_i) begin |
| state_d = Idle; |
| load_tcount = 1'b1; |
| tcount_sel = tNoDelay; |
| end else begin |
| state_d = Active; |
| load_tcount = 1'b1; |
| tcount_sel = tNoDelay; |
| end |
| end |
| |
| // AddrRead: read and compare target address |
| AddrRead : begin |
| if (bit_ack) begin |
| if (address_match) begin |
| state_d = AddrAckWait; |
| load_tcount = 1'b1; |
| tcount_sel = tClockStart; |
| end else state_d = Idle; |
| end |
| end |
| |
| // AddrAckWait: pause before acknowledging |
| AddrAckWait : begin |
| if (tcount_q == 20'd1) begin |
| state_d = AddrAckSetup; |
| end |
| end |
| // AddrAckSetup: target pulls SDA low while SCL is low |
| AddrAckSetup : begin |
| if (scl_i) state_d = AddrAckPulse; |
| end |
| // AddrAckPulse: target pulls SDA low while SCL is released |
| AddrAckPulse : begin |
| if (!scl_i) begin |
| state_d = AddrAckHold; |
| load_tcount = 1'b1; |
| tcount_sel = tClockStart; |
| end |
| end |
| // AddrAckHold: target pulls SDA low while SCL is pulled low |
| AddrAckHold : begin |
| if (tcount_q == 20'd1) begin |
| if (rw_bit) begin |
| if (tx_fifo_rvalid_i) begin |
| state_d = TransmitWait; |
| load_tcount = 1'b1; |
| tcount_sel = tClockLow; |
| end else state_d = StretchClock; |
| end else state_d = AcquireByte; |
| end |
| end |
| |
| // TransmitWait: pause before sending a bit |
| TransmitWait : begin |
| if (tcount_q == 20'd1) begin |
| state_d = TransmitSetup; |
| end |
| end |
| // TransmitSetup: target shifts indexed bit onto SDA while SCL is low |
| TransmitSetup : begin |
| if (scl_i) state_d = TransmitPulse; |
| end |
| // TransmitPulse: target shifts indexed bit onto SDA while SCL is released |
| TransmitPulse : begin |
| if (!scl_i) begin |
| state_d = TransmitHold; |
| load_tcount = 1'b1; |
| tcount_sel = tClockStart; |
| end |
| end |
| // TransmitHold: target shifts indexed bit onto SDA while SCL is pulled low |
| TransmitHold : begin |
| if (tcount_q == 20'd1) begin |
| load_tcount = 1'b1; |
| tcount_sel = tClockLow; |
| if (bit_ack) begin |
| state_d = TransmitAck; |
| end else begin |
| state_d = TransmitWait; |
| end |
| end |
| end |
| // TransmitAck: target waits for host to ACK transmission |
| TransmitAck : begin |
| if (scl_i) begin |
| if (host_ack) state_d = PopTxFifo; |
| else begin |
| if (start_det || stop_det) state_d = AcquireSrP; |
| end |
| end |
| end |
| |
| // PopTxFifo: populate tx_fifo |
| PopTxFifo : begin |
| if (!target_enable_i) begin |
| state_d = Idle; |
| end else if (tx_fifo_depth_i == 6'd1 && !tx_fifo_wvalid_i) begin |
| state_d = StretchClock; |
| end else begin |
| state_d = TransmitWait; |
| load_tcount = 1'b1; |
| tcount_sel = tClockLow; |
| end |
| end |
| |
| // StretchClock: target stretches the clock |
| StretchClock : begin |
| if (tx_fifo_depth_i == '0) begin |
| state_d = StretchClock; |
| end else begin |
| state_d = TransmitWait; |
| load_tcount = 1'b1; |
| tcount_sel = tClockLow; |
| end |
| end |
| |
| // AcquireByte: target acquires a byte |
| AcquireByte : begin |
| if (bit_ack) begin |
| state_d = AcquireAckWait; |
| load_tcount = 1'b1; |
| tcount_sel = tClockStart; |
| end |
| end |
| |
| // AcquireAckWait: pause before acknowledging |
| AcquireAckWait : begin |
| if (tcount_q == 20'd1) begin |
| state_d = AcquireAckSetup; |
| end |
| end |
| // AcquireAckSetup: target pulls SDA low while SCL is low |
| AcquireAckSetup : begin |
| if (scl_i) state_d = AcquireAckPulse; |
| end |
| // AcquireAckPulse: target pulls SDA low while SCL is released |
| AcquireAckPulse : begin |
| if (!scl_i) begin |
| state_d = AcquireAckHold; |
| load_tcount = 1'b1; |
| tcount_sel = tClockStart; |
| end |
| end |
| // AcquireAckHold: target pulls SDA low while SCL is pulled low |
| AcquireAckHold : begin |
| if (tcount_q == 20'd1) begin |
| if (bit_ack) begin |
| if (start_det || stop_det) state_d = AcquireSrP; |
| else state_d = AcquireByte; |
| end |
| end |
| end |
| |
| // AcquireSrP: target acquires repeated Start or Stop |
| AcquireSrP : begin |
| state_d = Idle; |
| end |
| |
| // default |
| default : begin |
| state_d = Idle; |
| load_tcount = 1'b0; |
| tcount_sel = tNoDelay; |
| bit_decr = 1'b0; |
| bit_clr = 1'b0; |
| byte_decr = 1'b0; |
| byte_clr = 1'b0; |
| read_byte_clr = 1'b0; |
| shift_data_en = 1'b0; |
| log_start = 1'b0; |
| log_stop = 1'b0; |
| restart = 1'b0; |
| input_byte_clr = 1'b0; |
| end |
| endcase |
| end |
| |
| // Synchronous state transition |
| always_ff @ (posedge clk_i or negedge rst_ni) begin : state_transition |
| if (!rst_ni) begin |
| state_q <= Idle; |
| end else begin |
| state_q <= state_d; |
| end |
| end |
| |
| // I2C bus outputs |
| assign scl_o = scl_temp; |
| assign sda_o = sda_temp; |
| |
| endmodule |
