Flash Write/read

[Altera_Forum]

Hi.. I am trying to write/ read from the flash. I am working on an Altera DE2 board. I am just trying to write some value (8-bit) in into a fixed memory location in a flash, and am trying to read it. I am able to read values from flash code but not able to write the values I want. 

 i.e The value being read is not the value I wrote in that memory, which shows that 'write' operation is not taking place.   I guess there are some series of operations to be performed before writing to a flash. I am not able to find any material on that.  Please help me out.. (attached below :code )   module flashcontroller( //REF_CLK, RESET_N, CLK, SW, SWIN, //controller outputs LEDR, FL_ADDR, FL_DQ, FL_CE_N, FL_OE_N, FL_WE_N, FL_RST_N, );   //input REF_CLK; input RESET_N; input CLK; input SW; input [7:0] SWIN; inout [7:0] FL_DQ ;  output [21:0] FL_ADDR;  output FL_CE_N; output FL_OE_N; output FL_WE_N; output FL_RST_N; output [7:0] LEDR;  wire[21:0] rFL_MAX; reg [21:0] rFL_ADDR;  reg [7:0] rFL_DQ; reg rFL_RST_N; reg [7:0] rLEDR; reg rFL_WE_N; reg rFL_OE_N; reg rFL_CE_N;  // assign rFL_MAX = 22'b1111111111111111111111; // assign FL_DQ = 8'b10000001; // assign FL_WE_N = 1'b1; // assign FL_OE_N = 1'b0; // assign FL_CE_N = 1'b0; assign FL_RST_N = rFL_RST_N; assign FL_ADDR = rFL_ADDR; assign LEDR = rLEDR; assign FL_DQ = rFL_DQ; assign FL_CE_N = rFL_CE_N; assign FL_OE_N = rFL_OE_N; assign FL_WE_N = rFL_WE_N;   always@(posedge CLK or negedge RESET_N) begin if (!RESET_N) begin rFL_RST_N <= 0; rFL_ADDR <= 0; end else if (SW == 1) begin rFL_RST_N <= 1; rFL_DQ <= 8'bz; rFL_WE_N <= 1'b1; rFL_OE_N <= 1'b0; rFL_CE_N <= 1'b0; rLEDR <= FL_DQ;   end else begin rFL_RST_N <= 1; rFL_WE_N <= 1'b0; rFL_OE_N <= 1'b1; rFL_CE_N <= 1'b0; rFL_DQ <= SWIN; rLEDR <= SWIN;   // rFL_RST_N <= 1; // if (rFL_ADDR > rFL_MAX) // begin // rFL_ADDR <= 0; // end // else // begin // rFL_ADDR <= rFL_ADDR+1; // end  end end endmodule

[Altera_Forum]

--- Quote Start ---  Hi.. I am trying to write/ read from the flash. I am working on an Altera DE2 board. I am just trying to write some value (8-bit) in into a fixed memory location in a flash, and am trying to read it. I am able to read values from flash code but not able to write the values I want. i.e The value being read is not the value I wrote in that memory, which shows that 'write' operation is not taking place.    --- Quote End ---   Are you using the correct flash write command or are you expecting the device behaves like a sram? Flash memory is not a sram: except reads, any other operation requires a special command sequence to be issued with a certain number of writes on specific addresses.    --- Quote Start ---   I guess there are some series of operations to be performed before writing to a flash. I am not able to find any material on that.   --- Quote End ---   Google the flash device part number and you'll find the datasheet. Read it and you'll get all the command codes for erase,write,identification,etc

[Altera_Forum]

Since I am working on the DE2 board, I don't have access to all the pins on the flash chip. For eg: I dont have access to BYTE pin and the RY/BY (ready/busy) pin.  

 I am saying this because the .csv file for the DE2 board does not contain these pin assignments. Hence, I want to know, whether write operation can be done without the use of these pins.   I have attached the datasheet for the flash, but cant find any such sequence.  Thanks

[Altera_Forum]

Since you do have the datasheet, I can't understand why you don't read it. 

Anyway: - byte pin selects 8 or 16bit bus; this is usually hardwired high or low depending on how the flash memory is connected to your system, i.e. if you have only 8 data bits connected or all 16. - ry/by is optional: you can get the same information reading the status bits. The command sequences are summarized in table 16, page 37.