Sending SPI signals to the Flash Memory through verilog FPGA controller, but not receiving anything from it, why does it happens?
Electrical Engineering Asked by user176257 on December 21, 2020
As a school project I want to write a very simple controller for a flash memory in a IC board. The FPGA chip is Altera 5CEFA4F23C8 and the flash is MX25L3206E.
I did an effort to produce the SCLK, SI and other signals that the chip needs through verilog, respecting the timing etc. I conceived the controller as a finite state machine that suppose to generate the SPI signals in order.
I have loaded the system to the board but it is not receiving anything from SO as I thought it would do automatically.
I’m using a “testbench-like” module that produce the avalon control, address and data signals like write, read and address, for a future implementation on a larger Avalon communication protocol SoC.
I’m adding the code I write for your reference.
module FLASH_CTL (
////////////// avalon interface///////////////////
input wire [23:0] avalon_slave_address,
input wire [3:0] avalon_slave_byteenable,
input wire avalon_slave_read, // .read
input wire avalon_slave_write, // .write
input wire [31:0] avalon_slave_writedata, // .writedata
input wire reset_sink_reset, // reset_sink.reset
input wire clock_sink_clk, // clock_sink_1.clk
output wire [31:0] avalon_slave_readdata, // .readdata
output wire avalon_slave_readdatavalid, // .readdatavalid
output wire avalon_slave_waitrequest, // .waitrequest
//////////////// chip interface ///////////////////
input wire SO,
output reg SI,
output reg CS,
output wire WP,
output wire HOLD,
output reg SCLK
);
parameter ST_0 = 4'd0; parameter ST_1 = 4'd1; parameter ST_2 = 4'd2; parameter ST_3 = 4'd3;
parameter ST_4 = 4'd4; parameter ST_5 = 4'd5; parameter ST_6 = 4'd6; parameter ST_7 = 4'd7;
parameter ST_8 = 4'd8; parameter ST_9 = 4'd9; parameter ST_10 = 4'd10; parameter ST_11 = 4'd11;
parameter wr_comm = 8'b0000_0010; // PROGRAM 0X02, write 0000_0010
parameter rd_comm = 8'b0000_0011; // PROGRAM 0X03, read 0000_0011
///////////////////////////////////////////////
parameter test_A = 8'b0001_1111;
reg [7:0] test_reg;
always@ (posedge clock_sink_clk or negedge reset_sink_reset) begin
if (~reset_sink_reset)
test_reg <= 0;
else
test_reg <= test_A;
end
////////////////////////////////////////////
reg [31:0] av_wrdata;
reg f_cyc_count, enable, rd_SO, f_bit_count, wr_mode, word_ak, clear_byte_c;
reg av_rd7, av_rd6, av_rd5, av_rd4, av_rd3, av_rd2, av_rd1, av_rd0;
reg [3:0] state, nextstate;
reg [4:0] cyc_count, byte_count;
reg [7:0] comm_in, data_in, av_rd_byte1, av_rd_byte2, av_rd_byte3, av_rd_byte4;
reg [23:0] addr_in;
reg [4:0] bit_count;
wire [7:0] av_rd_buff;
reg [2:0] bytes_enabled;
wire burstcount, debugaccess;
assign WP = 1;
assign HOLD = 1;
assign avalon_slave_waitrequest = ~ CS;
assign avalon_slave_readdatavalid = (CS && state >= 1 && wr_mode)? 1'b1:1'b0;
assign avalon_slave_readdata = {av_rd_byte1, av_rd_byte2, av_rd_byte3, av_rd_byte4};
assign av_rd_buff = {av_rd7, av_rd6, av_rd5, av_rd4, av_rd3, av_rd2, av_rd1, av_rd0};
assign burstcount = 0;
assign debugaccess = 0;
always@ (posedge clock_sink_clk or negedge reset_sink_reset)begin
if (~reset_sink_reset)
bytes_enabled <= 1;
else begin
bytes_enabled <= bytes_enabled;
case (avalon_slave_byteenable)
4'b0001: bytes_enabled <= 3'd0;
4'b0011: bytes_enabled <= 3'd1;
4'b0111: bytes_enabled <= 3'd2;
4'b1111: bytes_enabled <= 3'd3;
default: bytes_enabled <= bytes_enabled;
endcase
end
end
always@ (posedge clock_sink_clk or negedge reset_sink_reset)
if (~reset_sink_reset)
state <= ST_0;
else
state <= nextstate;
always@ (*) begin
CS <= 0; SI <= 0; SCLK <= 0; f_bit_count <= 0; f_cyc_count <= 0; rd_SO <= 0; word_ak <= 0; clear_byte_c <= 0;
case (state)
ST_0: begin
if (enable) begin
nextstate <= ST_1;
CS <= 0;
end
else begin
nextstate <= ST_0;
CS <= 1;
end
end
ST_1: begin
SI <= 0; // dont care
SCLK <= 1;
if (cyc_count == 10) begin
f_cyc_count <= 0;
nextstate <= ST_2;
end
else begin
f_cyc_count <= 1;
nextstate <= ST_1;
end
end
ST_2: begin ///// send command
SI <= comm_in [7 - bit_count];
SCLK <= 0;
if (cyc_count == 10) begin
f_cyc_count <= 0;
nextstate <= ST_3;
end
else begin
f_cyc_count <= 1;
nextstate <= ST_2;
end
end
ST_3: begin
SI <= comm_in [7 - bit_count];
SCLK <= 1;
if (cyc_count == 10) begin
f_cyc_count <= 0;
f_bit_count <= 1;
if (bit_count == 7) begin
nextstate <= ST_4;
word_ak <= 1;
clear_byte_c <= 1;
end
else begin
clear_byte_c <= 0;
nextstate = ST_2;
word_ak <= 0;
end
end
else begin
word_ak <= 0;
f_bit_count <= 0;
f_cyc_count <= 1;
nextstate <= ST_3;
end
end
ST_4: begin ///// send address
SI <= addr_in [23 - bit_count];
SCLK <= 0;
f_bit_count <= 0;
if (cyc_count == 10) begin
f_cyc_count <= 0;
nextstate <= ST_5;
end
else begin
f_cyc_count <= 1;
nextstate <= ST_4;
end
end
ST_5: begin
SI <= addr_in [23 - bit_count];
SCLK <= 1;
if (cyc_count == 10) begin
f_cyc_count <= 0;
f_bit_count <= 1;
if (bit_count == 23) begin
word_ak <= 1;
clear_byte_c <= 1;
if (wr_mode)
nextstate = ST_6;
else
nextstate = ST_9;
end
else begin
clear_byte_c <= 0;
nextstate = ST_4;
word_ak <= 0;
end
end
else begin
word_ak <= 0;
f_cyc_count <= 1;
nextstate <= ST_5;
end
end
ST_6: begin /// write
SI <= data_in [7 - bit_count];
SCLK <= 0;
f_bit_count <= 0;
if (cyc_count == 10) begin
f_cyc_count <= 0;
nextstate <= ST_7;
end
else begin
f_cyc_count <= 1;
nextstate <= ST_6;
end
end
ST_7: begin
SI <= data_in [7 - bit_count];
SCLK <= 1;
if (cyc_count == 10) begin
f_cyc_count <= 0;
f_bit_count <= 1;
if (bit_count == 7) begin
word_ak <= 1;
if (byte_count == bytes_enabled) begin
clear_byte_c <= 1;
nextstate <= ST_8;
end
else begin
clear_byte_c <= 0;
nextstate <= ST_6;
end
end
else begin
clear_byte_c <= 0;
word_ak <= 0;
nextstate = ST_6;
end
end
else begin
clear_byte_c <= 0;
word_ak <= 0;
f_bit_count <= 0;
f_cyc_count <= 1;
nextstate <= ST_7;
end
end
ST_8: begin
rd_SO <= 0;
CS <= 1;
if (cyc_count == 10) begin
f_cyc_count <= 0;
nextstate <= ST_0;
end
else begin
f_cyc_count <= 1;
nextstate <= ST_8;
end
end
///////
ST_9: begin
rd_SO <= 0; // read
SI <= 0;
SCLK <= 0;
f_bit_count <= 0;
if (cyc_count == 10) begin
f_cyc_count <= 0;
nextstate <= ST_10;
end
else begin
f_cyc_count <= 1;
nextstate <= ST_9;
end
end
ST_10: begin
rd_SO <= 1;
SI <= 0; // dont care
SCLK <= 1;
if (cyc_count == 10) begin
f_cyc_count <= 0;
f_bit_count <= 1;
if (bit_count == 7) begin
word_ak <= 1;
if (byte_count == bytes_enabled) begin
clear_byte_c <= 1;
nextstate <= ST_11;
end
else begin
clear_byte_c <= 0;
nextstate <= ST_9;
end
end
else begin
clear_byte_c <= 0;
word_ak <= 0;
nextstate = ST_9;
end
end
else begin
clear_byte_c <= 0;
word_ak <= 0;
f_bit_count <= 0;
f_cyc_count <= 1;
nextstate <= ST_10;
end
end
ST_11: begin
rd_SO <= 0;
CS <= 1;
if (cyc_count == 10) begin
f_cyc_count <= 0;
nextstate <= ST_0;
end
else begin
f_cyc_count <= 1;
nextstate <= ST_11;
end
end
default: begin
CS <= 0; SI <= 0; SCLK <= 0; f_bit_count <= 0; f_cyc_count <= 0; nextstate <= ST_0;
rd_SO <= 0; clear_byte_c <= 0;
end
endcase
end
always@(posedge clock_sink_clk or negedge reset_sink_reset) begin
if (~reset_sink_reset) begin
av_rd7 <= 0; av_rd6 <= 0; av_rd5 <= 0; av_rd4 <= 0;
av_rd3 <= 0;av_rd2 <= 0;av_rd1 <= 0;av_rd0 <= 0;
end
else if (rd_SO) begin
av_rd7 <= av_rd7; av_rd6 <= av_rd6; av_rd5 <= av_rd5; av_rd4 <= av_rd4;
av_rd3 <= av_rd3; av_rd2 <= av_rd2; av_rd1 <= av_rd1; av_rd0 <= av_rd0;
case (bit_count)
0: av_rd7 <= SO;
1: av_rd6 <= SO;
2: av_rd5 <= SO;
3: av_rd4 <= SO;
4: av_rd3 <= SO;
5: av_rd2 <= SO;
6: av_rd1 <= SO;
7: av_rd0 <= SO;
default: begin
av_rd7 <= av_rd7; av_rd6 <= av_rd6; av_rd5 <= av_rd5; av_rd4 <= av_rd4;
av_rd3 <= av_rd3; av_rd2 <= av_rd2; av_rd1 <= av_rd1; av_rd0 <= av_rd0;
end
endcase
end
else if (CS && state >= 1) begin
av_rd7 <= 0; av_rd6 <= 0; av_rd5 <= 0; av_rd4 <= 0;
av_rd3 <= 0;av_rd2 <= 0;av_rd1 <= 0;av_rd0 <= 0;
end
else begin
av_rd7 <= av_rd7; av_rd6 <= av_rd6; av_rd5 <= av_rd5; av_rd4 <= av_rd4;
av_rd3 <= av_rd3; av_rd2 <= av_rd2; av_rd1 <= av_rd1; av_rd0 <= av_rd0;
end
end
////////////////////////////////////////////////////////////////////////////
always@(posedge clock_sink_clk or negedge reset_sink_reset) begin // DESASOCIAR BIT_COUNT DE CYCLE COUNTER
if (~reset_sink_reset)
bit_count <= 0;
else if (word_ak)
bit_count <= 0;
else if (f_bit_count)
bit_count <= bit_count + 4'b1;
else
bit_count <= bit_count;
end
always@(posedge clock_sink_clk or negedge reset_sink_reset) begin
if (~reset_sink_reset)
cyc_count <= 0;
else if (f_cyc_count)
cyc_count <= cyc_count + 4'b1;
else
cyc_count <= 0;
end
always@(posedge clock_sink_clk or negedge reset_sink_reset) begin
if (~reset_sink_reset)
byte_count <= 0;
else if (CS && state >= 1)
byte_count <= 0;
else if (clear_byte_c)
byte_count <= 0;
else if (word_ak)
byte_count <= byte_count + 4'b1;
else
byte_count <= byte_count;
end
//////////////// Controls enable from write and read /////////////////////
always@(posedge clock_sink_clk or negedge reset_sink_reset) begin
if (~reset_sink_reset)
enable <= 0;
else if (avalon_slave_write || avalon_slave_read)
enable <= 1;
else
enable <= 0;
end
////// controls write vs read order, with priority write /////////////////
always@ (posedge clock_sink_clk or negedge reset_sink_reset) begin
if (~reset_sink_reset)
wr_mode <= 0;
else if (avalon_slave_write)
wr_mode <= 1;
else if (CS && state >= 1)
wr_mode <= 0;
else
wr_mode <= wr_mode;
end
///////////////////////////////////////////////////////////////////////
always@(posedge clock_sink_clk or negedge reset_sink_reset) begin
if (~reset_sink_reset)
comm_in <= rd_comm;
else if (avalon_slave_write)
comm_in <= wr_comm;
else if (avalon_slave_read)
comm_in <= rd_comm;
else
comm_in <= comm_in;
end
always@(posedge clock_sink_clk or negedge reset_sink_reset) begin
if (~reset_sink_reset)
addr_in <= 0;
else if (avalon_slave_write || avalon_slave_read )
addr_in <= avalon_slave_address;
else
addr_in <= addr_in;
end
always@(posedge clock_sink_clk or negedge reset_sink_reset) begin
if (~reset_sink_reset)
av_wrdata <= 0;
else if (avalon_slave_write || avalon_slave_read )
av_wrdata <= avalon_slave_writedata;
else
av_wrdata <= av_wrdata;
end
always@(posedge clock_sink_clk or negedge reset_sink_reset) begin
if (~reset_sink_reset)
data_in <= avalon_slave_writedata [7:0];
else
case (byte_count)
0: data_in <= av_wrdata [7:0];
1: data_in <= av_wrdata[15:8];
2: data_in <= av_wrdata [23:16];
3: data_in <= av_wrdata [31:24];
default: data_in <= av_wrdata [7:0];
endcase
end
///////// Gather all 4 bytes in 1 register ////////////////////////
always@(posedge clock_sink_clk or negedge reset_sink_reset) begin
if (~reset_sink_reset) begin
av_rd_byte1 <= 0; av_rd_byte2 <= 0; av_rd_byte3 <= 0; av_rd_byte4 <= 0;
end
else if (clear_byte_c && state >= ST_10) begin
av_rd_byte1 <= av_rd_byte1; av_rd_byte2 <= av_rd_byte2; av_rd_byte3 <= av_rd_byte3; av_rd_byte4 <= av_rd_byte4;
case (byte_count)
0: av_rd_byte1 <= av_rd_buff;
1: av_rd_byte2 <= av_rd_buff;
2: av_rd_byte3 <= av_rd_buff;
3: av_rd_byte4 <= av_rd_buff;
default: begin
av_rd7 <= av_rd7; av_rd6 <= av_rd6; av_rd5 <= av_rd5; av_rd4 <= av_rd4;
av_rd3 <= av_rd3; av_rd2 <= av_rd2; av_rd1 <= av_rd1; av_rd0 <= av_rd0;
end
endcase
end
else if (CS && state >= 1) begin
av_rd_byte1 <= 0; av_rd_byte2 <= 0; av_rd_byte3 <= 0; av_rd_byte4 <= 0;
end
end
endmodule
The top module is this
module FLASH_CTL_TOP (
input wire sys_rst, // reset_sink.reset
input wire sys_clk, // clock_sink_1.clk
//////////////// chip interface ///////////////////
input wire SO,
output wire SI,
output wire CS,
output wire WP,
output wire HOLD,
output wire SCLK ,
output reg led
);
reg [23:0] avalon_slave_address;// avalon_slave.address ?????????????????????????
reg [3:0] avalon_slave_byteenable; // .byteenable
reg avalon_slave_read; // .read
reg avalon_slave_write; // .write
reg [31:0] avalon_slave_writedata; // .writedata
reg [14:0] tb_count;
wire [31:0] avalon_slave_readdata; // .readdata
wire avalon_slave_readdatavalid; // .readdatavalid
wire avalon_slave_waitrequest; // .waitrequest
wire debugaccess, burstcount;
assign burstcount = 0;
assign debugaccess = 0;
reg [31:0] led_counter;
/*
flash_qsys u0 (
.clk_clk (sys_clk), // clk.clk
.reset_reset_n (sys_rst), // reset.reset_n
.end_cs (CS), // end.cs
.end_si (SI), // .si
.end_so (SO), // .so
.end_wp (WP), // .wp
.end_sclk (SCLK), // .sclk
.end_hold (HOLD), // .hold
.sobus_waitrequest (avalon_slave_waitrequest), // sobus.waitrequest
.sobus_readdata (avalon_slave_readdata), // .readdata
.sobus_readdatavalid (avalon_slave_readdatavalid), // .readdatavalid
.sobus_burstcount (burstcount), // .burstcount
.sobus_writedata (avalon_slave_writedata), // .writedata
.sobus_address (avalon_slave_address), // .address
.sobus_write (avalon_slave_write), // .write
.sobus_read (avalon_slave_read), // .read
.sobus_byteenable (avalon_slave_byteenable), // .byteenable
.sobus_debugaccess (debugaccess) // .debugaccess
);
*/
FLASH_CTL FLASH_CTL_inst1 (
.SO (SO),
.SI (SI),
.CS(CS),
.WP(WP),
.HOLD(HOLD),
.SCLK(SCLK),
.avalon_slave_address (avalon_slave_address),
.avalon_slave_byteenable (avalon_slave_byteenable),
.avalon_slave_read (avalon_slave_read),
.avalon_slave_write (avalon_slave_write ),
.avalon_slave_writedata (avalon_slave_writedata),
.reset_sink_reset (sys_rst),
.clock_sink_clk (sys_clk),
.avalon_slave_readdata (avalon_slave_readdata),
.avalon_slave_readdatavalid (avalon_slave_readdatavalid),
.avalon_slave_waitrequest (avalon_slave_waitrequest)
);
always@(posedge sys_clk or negedge sys_rst) begin
if (~sys_rst) begin
led <= 1;
led_counter <= 0;
end
else if (led_counter == 31'd100_000_000) begin
led <= 0;
led_counter <= led_counter + 16'b1;;
end
else if (led_counter == 31'd200_000_000) begin
led <= 1;
led_counter <= 0;
end
else begin
led <= led;
led_counter <= led_counter + 16'b1;
end
end
always@(posedge sys_clk or negedge sys_rst) begin
if (~sys_rst) begin
avalon_slave_read <= 0;
avalon_slave_write <= 0;
avalon_slave_address <= 0;
avalon_slave_writedata <= 0;
avalon_slave_byteenable <= 0;
end
else if (tb_count == 200) begin
avalon_slave_write <= 1;
avalon_slave_read <= 0;
avalon_slave_address <= 24'b0000_0000_0000_0000_0000_0011; //// 24'b0000_0000_0000_0000_0000_0011
avalon_slave_writedata <= 32'b1010_1010_1010_0000__0000_0000_0000_0011; //8'b1000_0101
avalon_slave_byteenable <= 4'b1111;
end
else if (tb_count == 2000) begin
avalon_slave_read <= 1;
avalon_slave_write <= 0;
avalon_slave_address <= 24'b0000_0000_0000_0000_0000_0011; //// 24'b0000_0000_0000_0000_0000_0011
avalon_slave_writedata <= 32'b0000_0000_0000_0000__0000_0000_0000_0000; // 8'b0000_0000
avalon_slave_byteenable <= 4'b1111;
end
else begin
avalon_slave_byteenable <= 0;
avalon_slave_read <= 0;
avalon_slave_write <= 0;
avalon_slave_address <= 0;
avalon_slave_writedata <= 0;
end
end
always@ (posedge sys_clk or negedge sys_rst) begin
if (~sys_rst)
tb_count <= 0;
else if (tb_count == 3000)
tb_count <= tb_count;
else
tb_count <= tb_count + 15'b1;
end
endmodule
The code is basically running as expected (as far as I know) as it can be seen in the second attached imag, but I’m receiving this “1” from the SO pin from the beginning of the time without changes, so I’m not able to pick up the “supposedly” data from SO.
any thoughts about this? Chip might be malfunctioning?
One Answer
I wonder why your trace doesn't have SI signaling? A SPI Flash memory is not a simple device, it needs status checking and likely some mode selection commands to start operating. Where is CS# in your traces? What is HOLD# status? From datasheet:
DEVICE OPERATION
1.Before a command is issued, status register should be checked to ensure device is ready for the intended operation.
2.When incorrect command is inputted to this device, it enters standby mode and remains in standby mode until next CS# falling edge. In standby mode, SO pin of the device is High-Z. The CS# falling time needs to follow tCHCL spec.
3.When correct command is inputted to this device, it enters active mode and remains in active mode until next CS# rising edge. The CS# rising time needs to follow tCLCH spec.
4.Input data is latched on the rising edge of Serial Clock(SCLK) and data is shifted out on the falling edge of SCLK. The difference of Serial mode 0 and mode 3 is shown in Figure 1.
5.For the following instructions: RDID, RDSR, RDSCUR, READ, FAST_READ, RDSFDP, DREAD, RES, and REMS the shifted-in instruction sequence is followed by a data-out sequence. After any bit of data being shifted out, the CS# can be high. For the following instructions: WREN, WRDI, WRSR, SE, BE, CE, PP, RDP, DP, ENSO, EXSO, and WRSCUR, the CS# must go high exactly at the byte boundary; otherwise, the instruction will be rejected and not executed.
6.While a Write Status Register, Program, or Erase operation is in progress, access to the memory array is neglected and will not affect the current operation of Write Status Register, Program, Erase
Which command are you sending to your memory chip?
Answered by Ale..chenski on December 21, 2020
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