/*
* Copyright 2021 Dennis Potter <dennis@dennispotter.eu>
*
* Permission is hereby granted, free of charge, to any person
* obtaining a copy of this software and associated documentation
* files (the "Software"), to deal in the Software without
* restriction, including without limitation the rights to use,
* copy, modify, merge, publish, distribute, sublicense, and/or
* sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following
* conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
* OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
* HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
* WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
* OTHER DEALINGS IN THE SOFTWARE.
*/
module srdl2sv_amba3ahblite #(
parameter bit FLOP_REGISTER_IF = 0,
parameter BUS_BITS = 32,
parameter NO_BYTE_ENABLE = 0
)
(
// Bus protocol
input HCLK,
input HRESETn,
input HSEL,
input [31:0] HADDR,
input HWRITE,
input [ 2:0] HSIZE,
input [ 3:0] HPROT, // Might be used in the future together with an RDL UDP
input [ 1:0] HTRANS,
input [BUS_BITS-1:0] HWDATA,
output logic HREADYOUT,
output logic HRESP,
output logic [BUS_BITS-1:0] HRDATA,
// Interface to internal logic
srdl2sv_widget_if.widget widget_if
);
localparam BUS_BYTES = BUS_BITS/8;
localparam BUS_BYTES_W = $clog2(BUS_BYTES);
/***********************
* Define enums
***********************/
typedef enum logic [2:0] {
SINGLE = 3'b000,
INCR = 3'b001,
WRAP4 = 3'b010,
INCR4 = 3'b011,
WRAP8 = 3'b100,
INCR8 = 3'b101,
WRAP16 = 3'b110,
INCR16 = 3'b111
} HBURST_t;
typedef enum logic [1:0] {
IDLE = 2'b00,
BUSY = 2'b01,
NONSEQ = 2'b10,
SEQ = 2'b11
} HTRANS_t;
typedef enum logic {
OKAY = 1'b0,
ERROR = 1'b1
} HRESP_t;
typedef enum logic {
READ = 1'b0,
WRITE = 1'b1
} OP_t;
typedef enum logic [1:0] {
FSM_IDLE = 2'b00,
FSM_TRANS = 2'b01,
FSM_ERR_0 = 2'b10,
FSM_ERR_1 = 2'b11
} fsm_t;
/****************************
* Determine current address
****************************/
logic [31:0] HADDR_q;
logic [2:0] HSIZE_q;
OP_t operation_q;
wire addr_err = HADDR % (32'b1 << HSIZE) != 32'b0;
always_ff @ (posedge HCLK)
begin
case (HTRANS)
IDLE: ;// Do nothing
BUSY: ;// Do nothing
NONSEQ:
begin
// When a transfer is extended it has the side-effecxt
// of extending the address phase of the next transfer
if (HREADYOUT)
begin
HADDR_q <= HADDR;
HSIZE_q <= HSIZE;
operation_q <= HWRITE ? WRITE : READ;
end
end
SEQ:
begin
if (HREADYOUT)
begin
HADDR_q <= HADDR;
HSIZE_q <= HSIZE;
end
end
endcase
end
/****************************
* Statemachine
****************************/
logic [BUS_BITS-1:0] HRDATA_temp;
fsm_t fsm_next, fsm_q;
always_comb
begin
// Defaults
HREADYOUT = 1'b1;
HRESP = OKAY;
// When reading back, the data of the bit that was accessed over the bus
// should be at byte 0 of the HRDATA bus and bits that were not accessed
// should be masked with 0s.
HRDATA_temp = widget_if.r_data >> (8*HADDR_q[BUS_BYTES_W-1:0]);
for (int i = 0; i < BUS_BYTES; i++)
if (i < (1 << HSIZE_q))
HRDATA[8*(i+1)-1 -: 8] = HRDATA_temp[8*(i+1)-1 -: 8];
else
HRDATA[8*(i+1)-1 -: 8] = 8'b0;
widget_if_w_vld_next = 0;
widget_if_r_vld_next = 0;
fsm_next = fsm_q;
case (fsm_q)
default: // FSM_IDLE
begin
if (HSEL && HTRANS > BUSY)
begin
if (addr_err)
// In case the address is illegal, switch to an error state
fsm_next = FSM_ERR_0;
else if (HTRANS == NONSEQ)
// If NONSEQ, go to NONSEQ state
fsm_next = FSM_TRANS;
else if (HTRANS == SEQ)
// If a SEQ is provided, something is wrong
fsm_next = FSM_ERR_0;
end
end
FSM_TRANS:
begin
HREADYOUT = widget_if.rdy;
widget_if_w_vld_next = operation_q == WRITE;
widget_if_r_vld_next = operation_q == READ;
if (HTRANS == BUSY)
begin
// Wait
fsm_next = FSM_TRANS;
end
else if (widget_if.err && widget_if.rdy)
begin
HREADYOUT = 0;
HRESP = ERROR;
fsm_next = FSM_ERR_1;
end
else if (HTRANS == NONSEQ)
begin
// Another unrelated access is coming
fsm_next = FSM_TRANS;
end
else if (HTRANS == SEQ)
begin
// Another part of the burst is coming
fsm_next = FSM_TRANS;
end
else if (HTRANS == IDLE)
begin
// All done, wrapping things up!
fsm_next = widget_if.rdy ? FSM_IDLE : FSM_TRANS;
end
end
FSM_ERR_0:
begin
HREADYOUT = 0;
if (HTRANS == BUSY)
begin
// Slaves must always provide a zero wait state OKAY response
// to BUSY transfers and the transfer must be ignored by the slave.
HRESP = OKAY;
fsm_next = FSM_ERR_0;
end
else
begin
HRESP = ERROR;
fsm_next = FSM_ERR_1;
end
end
FSM_ERR_1:
begin
if (HTRANS == BUSY)
begin
// Slaves must always provide a zero wait state OKAY response
// to BUSY transfers and the transfer must be ignored by the slave.
HREADYOUT = 0;
HRESP = OKAY;
fsm_next = FSM_ERR_0;
end
else
begin
HREADYOUT = 1;
HRESP = ERROR;
fsm_next = FSM_IDLE;
end
end
endcase
end
always_ff @ (posedge HCLK or negedge HRESETn)
if (!HRESETn)
fsm_q <= FSM_IDLE;
else
fsm_q <= fsm_next;
/***
* Determine the number of active bytes
***/
logic [BUS_BYTES-1:0] HSIZE_bitfielded;
logic [BUS_BYTES-1:0] widget_if_byte_en_next;
logic widget_if_w_vld_next;
logic widget_if_r_vld_next;
generate
if (NO_BYTE_ENABLE)
begin
assign widget_if_byte_en_next = {BUS_BYTES{1'b1}};
end
else
begin
always_comb
begin
for (int i = 0; i < BUS_BYTES; i++)
HSIZE_bitfielded[i] = i < (1 << HSIZE_q);
// Shift if not the full bus is accessed
widget_if_byte_en_next = HSIZE_bitfielded << (HADDR_q % BUS_BYTES);
end
end
endgenerate
/***
* Drive interface to registers
***/
generate
if (FLOP_REGISTER_IF)
begin
always_ff @ (posedge HCLK or negedge HRESETn)
if (!HRESETn)
begin
widget_if.w_vld <= 1'b0;
widget_if.r_vld <= 1'b0;
end
else
begin
widget_if.w_vld <= widget_if_w_vld_next;
widget_if.r_vld <= widget_if_r_vld_next;
end
always_ff @ (posedge HCLK)
begin
widget_if.addr <= {HADDR_q[31:BUS_BYTES_W], {BUS_BYTES_W{1'b0}}};
widget_if.w_data <= HWDATA << (8*HADDR_q[BUS_BYTES_W-1:0]);
widget_if.byte_en <= widget_if_byte_en_next;
end
end
else
begin
assign widget_if.w_vld = widget_if_w_vld_next;
assign widget_if.r_vld = widget_if_r_vld_next;
assign widget_if.addr = {HADDR_q[31:BUS_BYTES_W], {BUS_BYTES_W{1'b0}}};
assign widget_if.w_data = HWDATA << (8*HADDR_q[BUS_BYTES_W-1:0]);
assign widget_if.byte_en = widget_if_byte_en_next;
end
endgenerate
endmodule