`timescale 1ns / 1ps
module novena_fmc_top
(
input wire gclk_p_pin,
input wire gclk_n_pin,
input wire reset_mcu_b_pin,
input wire fmc_clk, // clock
input wire [21: 0] fmc_a, // address
inout wire [31: 0] fmc_d, // data
input wire fmc_ne1, // chip select
input wire fmc_noe, // output enable
input wire fmc_nwe, // write enable
input wire fmc_nl, // latch enable
output wire fmc_nwait, // wait
output wire apoptosis_pin,
output wire led_pin
);
//
// Clock Manager
//
wire sys_clk;
wire sys_rst;
novena_clkmgr_new #
(
.CLK_OUT_MUL (2), // 2..32
.CLK_OUT_DIV (2) // 1..32
)
clkmgr
(
.gclk_p (gclk_p_pin),
.gclk_n (gclk_n_pin),
.reset_mcu_b (reset_mcu_b_pin),
.sys_clk (sys_clk),
.sys_rst (sys_rst)
);
//
// BUFG
//
wire fmc_clk_bug;
BUFG BUFG_fmc_clk
(
.I (fmc_clk),
.O (fmc_clk_bufg)
);
//----------------------------------------------------------------
// FMC Arbiter
//
// FMC arbiter handles FMC access and transfers it into
// `sys_clk' clock domain.
//----------------------------------------------------------------
wire [21: 0] sys_fmc_addr; // address
wire sys_fmc_wren; // write enable
wire sys_fmc_rden; // read enable
wire [31: 0] sys_fmc_dout; // data output (from STM32 to FPGA)
reg [31: 0] sys_fmc_din; // data input (from FPGA to STM32)
fmc_arbiter #
(
.NUM_ADDR_BITS(22) // change to 26 when
)
fmc
(
.fmc_clk(fmc_clk_bufg),
.fmc_a(fmc_a),
.fmc_d(fmc_d),
.fmc_ne1(fmc_ne1),
.fmc_nl(fmc_nl),
.fmc_nwe(fmc_nwe),
.fmc_noe(fmc_noe),
.fmc_nwait(fmc_nwait),
.sys_clk(sys_clk),
.sys_addr(sys_fmc_addr),
.sys_wr_en(sys_fmc_wren),
.sys_rd_en(sys_fmc_rden),
.sys_data_out(sys_fmc_dout),
.sys_data_in(sys_fmc_din)
);
//----------------------------------------------------------------
// Dummy Register
//
// General-purpose register to test FMC interface using STM32
// demo program instead of core selector logic.
//
// This register is a bit tricky, but it allows testing of both
// data and address buses. Reading from FPGA will always return
// value, which is currently stored in the test register,
// regardless of read transaction address. Writing to FPGA has
// two variants: a) writing to address 0 will store output data
// data value in the test register, b) writing to any non-zero
// address will store _address_ of write transaction in the test
// register.
//
// To test data bus, write some different patterns to address 0,
// then readback from any address and compare.
//
// To test address bus, write anything to some different non-zero
// addresses, then readback from any address and compare returned
// value with previously written address.
//
//----------------------------------------------------------------
reg [31: 0] test_reg;
always @(posedge sys_clk)
//
if (sys_fmc_wren) begin
//
// when writing to address 0, store input data value
//
// when writing to non-zero address, store _address_
// (padded with zeroes) instead of data
//
test_reg <= (sys_fmc_addr == {22{1'b0}}) ? sys_fmc_dout : {{10{1'b0}}, sys_fmc_addr};
//
end else if (sys_fmc_rden) begin
//
// always return current value, ignore address
//
sys_fmc_din <= test_reg;
//
end
//----------------------------------------------------------------
// LED Driver
//
// A simple utility LED driver that turns on the Novena
// board LED when the FMC interface is active.
//----------------------------------------------------------------
fmc_indicator led
(
.sys_clk(sys_clk),
.sys_rst(sys_rst),
.fmc_active(sys_fmc_wren | sys_fmc_rden),
.led_out(led_pin)
);
//----------------------------------------------------------------
// Novena Patch
//
// Patch logic to keep the Novena board happy.
// The apoptosis_pin pin must be kept low or the whole board
// (more exactly the CPU) will be reset after the FPGA has
// been configured.
//----------------------------------------------------------------
assign apoptosis_pin = 1'b0;
endmodule
