////////////////////////////////////////////////////////////////////////////////
//
//
// Filename: wbdmac.v
//
// Project: Zip CPU -- a small, lightweight, RISC CPU soft core
//
// Purpose: Wishbone DMA controller
//
// This module is controllable via the wishbone, and moves values from
// one location in the wishbone address space to another. The amount of
// memory moved at any given time can be up to 4kB, or equivalently 1kW.
// Four registers control this DMA controller: a control/status register,
// a length register, a source WB address and a destination WB address.
// These register may be read at any time, but they may only be written
// to when the controller is idle.
//
// The meanings of three of the setup registers should be self explanatory:
// - The length register controls the total number of words to
// transfer.
// - The source address register controls where the DMA controller
// reads from. This address may or may not be incremented
// after each read, depending upon the setting in the
// control/status register.
// - The destination address register, which controls where the DMA
// controller writes to. This address may or may not be
// incremented after each write, also depending upon the
// setting in the control/status register.
//
// It is the control/status register, at local address zero, that needs
// more definition:
//
// Bits:
// 31 R Write protect If this is set to one, it means the
// write protect bit is set and the controller
// is therefore idle. This bit will be set upon
// completing any transfer.
// 30 R Error. The controller stopped mid-transfer
// after receiving a bus error.
// 29 R/W inc_s_n If set to one, the source address
// will not increment from one read to the next.
// 28 R/W inc_d_n If set to one, the destination address
// will not increment from one write to the next.
// 27 R Always 0
// 26..16 R nread Indicates how many words have been read,
// and not necessarily written (yet). This
// combined with the cfg_len parameter should tell
// exactly where the controller is at mid-transfer.
// 27..16 W WriteProtect When a 12'h3db is written to these
// bits, the write protect bit will be cleared.
//
// 15 R/W on_dev_trigger When set to '1', the controller will
// wait for an external interrupt before starting.
// 14..10 R/W device_id This determines which external interrupt
// will trigger a transfer.
// 9..0 R/W transfer_len How many bytes to transfer at one time.
// The minimum transfer length is one, while zero
// is mapped to a transfer length of 1kW.
//
//
// To use this, follow this checklist:
// 1. Wait for any prior DMA operation to complete
// (Read address 0, wait 'till either top bit is set or cfg_len==0)
// 2. Write values into length, source and destination address.
// (writei(3, &vals) should be sufficient for this.)
// 3. Enable the DMAC interrupt in whatever interrupt controller is present
// on the system.
// 4. Write the final start command to the setup/control/status register:
// Set inc_s_n, inc_d_n, on_dev_trigger, dev_trigger,
// appropriately for your task
// Write 12'h3db to the upper word.
// Set the lower word to either all zeros, or a smaller transfer
// length if desired.
// 5. wait() for the interrupt and the operation to complete.
// Prior to completion, number of items successfully transferred
// be read from the length register. If the internal buffer is
// being used, then you can read how much has been read into that
// buffer by reading from bits 25..16 of this control/status
// register.
//
// Creator: Dan Gisselquist
// Gisselquist Technology, LLC
//
////////////////////////////////////////////////////////////////////////////////
//
// Copyright (C) 2015-2016, Gisselquist Technology, LLC
//
// This program is free software (firmware): you can redistribute it and/or
// modify it under the terms of the GNU General Public License as published
// by the Free Software Foundation, either version 3 of the License, or (at
// your option) any later version.
//
// This program is distributed in the hope that it will be useful, but WITHOUT
// ANY WARRANTY; without even the implied warranty of MERCHANTIBILITY or
// FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
// for more details.
//
// License: GPL, v3, as defined and found on www.gnu.org,
// http://www.gnu.org/licenses/gpl.html
//
//
///////////////////////////////////////////////////////////////////////////
//
//
`define DMA_IDLE 3'b000
`define DMA_WAIT 3'b001
`define DMA_READ_REQ 3'b010
`define DMA_READ_ACK 3'b011
`define DMA_PRE_WRITE 3'b100
`define DMA_WRITE_REQ 3'b101
`define DMA_WRITE_ACK 3'b110
module wbdmac(i_clk, i_rst,
i_swb_cyc, i_swb_stb, i_swb_we, i_swb_addr, i_swb_data,
o_swb_ack, o_swb_stall, o_swb_data,
o_mwb_cyc, o_mwb_stb, o_mwb_we, o_mwb_addr, o_mwb_data,
i_mwb_ack, i_mwb_stall, i_mwb_data, i_mwb_err,
i_dev_ints,
o_interrupt);
parameter ADDRESS_WIDTH=32, LGMEMLEN = 10,
DW=32, LGDV=5,AW=ADDRESS_WIDTH;
input i_clk, i_rst;
// Slave/control wishbone inputs
input i_swb_cyc, i_swb_stb, i_swb_we;
input [1:0] i_swb_addr;
input [(DW-1):0] i_swb_data;
// Slave/control wishbone outputs
output reg o_swb_ack;
output wire o_swb_stall;
output reg [(DW-1):0] o_swb_data;
// Master/DMA wishbone control
output wire o_mwb_cyc, o_mwb_stb, o_mwb_we;
output reg [(AW-1):0] o_mwb_addr;
output reg [(DW-1):0] o_mwb_data;
// Master/DMA wishbone responses from the bus
input i_mwb_ack, i_mwb_stall;
input [(DW-1):0] i_mwb_data;
input i_mwb_err;
// The interrupt device interrupt lines
input [(DW-1):0] i_dev_ints;
// An interrupt to be set upon completion
output reg o_interrupt;
// Need to release the bus for a higher priority user
// This logic had lots of problems, so it is being
// removed. If you want to make sure the bus is available
// for a higher priority user, adjust the transfer length
// accordingly.
//
// input i_other_busmaster_requests_bus;
//
reg [2:0] dma_state;
reg cfg_err, cfg_len_nonzero;
reg [(AW-1):0] cfg_waddr, cfg_raddr, cfg_len;
reg [(LGMEMLEN-1):0] cfg_blocklen_sub_one;
reg cfg_incs, cfg_incd;
reg [(LGDV-1):0] cfg_dev_trigger;
reg cfg_on_dev_trigger;
// Single block operations: We'll read, then write, up to a single
// memory block here.
reg [(DW-1):0] dma_mem [0:(((1<= nread-1);
else
last_write_request <= (nwritten >= nread-2);
end else
last_write_request <= 1'b0;
initial last_write_ack = 1'b0;
always @(posedge i_clk)
if((dma_state == `DMA_WRITE_REQ)||(dma_state == `DMA_WRITE_ACK))
begin
if ((i_mwb_ack)&&((~o_mwb_stb)||(i_mwb_stall)))
last_write_ack <= (nwacks+2 == nwritten);
else
last_write_ack <= (nwacks+1 == nwritten);
end else
last_write_ack <= 1'b0;
assign o_mwb_cyc = (dma_state == `DMA_READ_REQ)
||(dma_state == `DMA_READ_ACK)
||(dma_state == `DMA_WRITE_REQ)
||(dma_state == `DMA_WRITE_ACK);
assign o_mwb_stb = (dma_state == `DMA_READ_REQ)
||(dma_state == `DMA_WRITE_REQ);
assign o_mwb_we = (dma_state == `DMA_PRE_WRITE)
||(dma_state == `DMA_WRITE_REQ)
||(dma_state == `DMA_WRITE_ACK);
//
// This is tricky. In order for Vivado to consider dma_mem to be a
// proper memory, it must have a simple address fed into it. Hence
// the read_address (rdaddr) register. The problem is that this
// register must always be one greater than the address we actually
// want to read from, unless we are idling. So ... the math is touchy.
//
reg [(LGMEMLEN-1):0] rdaddr;
always @(posedge i_clk)
if((dma_state == `DMA_IDLE)||(dma_state == `DMA_WAIT)
||(dma_state == `DMA_WRITE_ACK))
rdaddr <= 0;
else if ((dma_state == `DMA_PRE_WRITE)
||((dma_state==`DMA_WRITE_REQ)&&(~i_mwb_stall)))
rdaddr <= rdaddr + {{(LGMEMLEN-1){1'b0}},1'b1};
always @(posedge i_clk)
if ((dma_state != `DMA_WRITE_REQ)||(~i_mwb_stall))
o_mwb_data <= dma_mem[rdaddr];
always @(posedge i_clk)
if((dma_state == `DMA_READ_REQ)||(dma_state == `DMA_READ_ACK))
dma_mem[nread[(LGMEMLEN-1):0]] <= i_mwb_data;
always @(posedge i_clk)
casez(i_swb_addr)
2'b00: o_swb_data <= { (dma_state != `DMA_IDLE), cfg_err,
~cfg_incs, ~cfg_incd,
1'b0, nread,
cfg_on_dev_trigger, cfg_dev_trigger,
cfg_blocklen_sub_one
};
2'b01: o_swb_data <= { {(DW-AW){1'b0}}, cfg_len };
2'b10: o_swb_data <= { {(DW-AW){1'b0}}, cfg_raddr};
2'b11: o_swb_data <= { {(DW-AW){1'b0}}, cfg_waddr};
endcase
// This causes us to wait a minimum of two clocks before starting: One
// to go into the wait state, and then one while in the wait state to
// develop the trigger.
initial trigger = 1'b0;
always @(posedge i_clk)
trigger <= (dma_state == `DMA_WAIT)
&&((~cfg_on_dev_trigger)
||(i_dev_ints[cfg_dev_trigger]));
// Ack any access. We'll quietly ignore any access where we are busy,
// but ack it anyway. In other words, before writing to the device,
// double check that it isn't busy, and then write.
always @(posedge i_clk)
o_swb_ack <= (i_swb_stb);
assign o_swb_stall = 1'b0;
initial abort = 1'b0;
always @(posedge i_clk)
abort <= (i_rst)||((i_swb_stb)&&(i_swb_we)
&&(i_swb_addr == 2'b00)
&&(i_swb_data == 32'hffed0000));
endmodule