mirror of
https://github.com/garrettsworkshop/RAM2GS.git
synced 2024-12-01 10:49:51 +00:00
411 lines
15 KiB
Verilog
411 lines
15 KiB
Verilog
module RAM2GS(PHI2, MAin, CROW, Din, Dout,
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nCCAS, nCRAS, nFWE, LED,
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RBA, RA, RD, nRCS, RCLK, RCKE,
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nRWE, nRRAS, nRCAS, RDQMH, RDQML,
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nUFMCS, UFMCLK, UFMSDI, UFMSDO);
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/* 65816 Phase 2 Clock */
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input PHI2;
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/* Async. DRAM Control Inputs */
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input nCCAS, nCRAS;
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/* Synchronized PHI2 and DRAM signals */
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reg PHI2r, PHI2r2, PHI2r3;
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reg RASr, RASr2, RASr3;
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reg CASr, CASr2, CASr3;
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reg FWEr;
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reg CBR;
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/* Activity LED */
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reg LEDEN;
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output LED;
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assign LED = !(!nCRAS && !CBR && LEDEN && Ready);
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/* 65816 Data */
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input [7:0] Din;
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output [7:0] Dout;
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assign Dout[7:0] = RD[7:0];
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/* Latched 65816 Bank Address */
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reg [7:0] Bank;
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/* Async. DRAM Address Bus */
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input [1:0] CROW;
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input [9:0] MAin;
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input nFWE;
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reg n8MEGEN = 0;
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reg XOR8MEG = 0;
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/* SDRAM Clock */
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input RCLK;
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/* SDRAM */
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reg RCKEEN;
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output reg RCKE = 0;
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output reg nRCS = 1, nRRAS = 1, nRCAS = 1, nRWE = 1;
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output reg [1:0] RBA;
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reg nRowColSel;
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reg RA11;
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reg RA10;
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reg [9:0] RowA;
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output [11:0] RA;
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assign RA[11] = RA11;
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assign RA[10] = RA10;
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assign RA[9:0] = !nRowColSel ? RowA[9:0] : MAin[9:0];
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output RDQML, RDQMH;
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assign RDQML = !nRowColSel ? 1'b1 : !MAin[9];
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assign RDQMH = !nRowColSel ? 1'b1 : MAin[9];
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reg [7:0] WRD;
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inout [7:0] RD;
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assign RD[7:0] = (!nCCAS && !nFWE) ? WRD[7:0] : 8'bZ;
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/* UFM Interface */
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output reg nUFMCS = 1;
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output reg UFMCLK = 0;
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output reg UFMSDI = 0;
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input UFMSDO;
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/* UFM Command Interface */
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reg C1Submitted = 0;
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reg ADSubmitted = 0;
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reg CmdEnable = 0;
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reg CmdSubmitted = 0;
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reg Cmdn8MEGEN = 0;
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reg CmdLEDEN = 0;
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reg CmdUFMCLK = 0;
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reg CmdUFMSDI = 0;
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reg CmdUFMCS = 0;
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wire ADWR = Bank[7:0]==8'hFB && MAin[7:0]==8'hFF && !nFWE;
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wire C1WR = Bank[7:0]==8'hFB && MAin[7:0]==8'hFE && !nFWE;
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wire CMDWR = Bank[7:0]==8'hFB && MAin[7:0]==8'hFD && !nFWE;
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/* State Counters */
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reg InitReady = 0; // 1 if ready for init sequence
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reg Ready = 0; // 1 if done with init sequence
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reg [1:0] S = 0; // post-RAS State counter
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reg [17:0] FS = 0; // Fast init state counter
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reg [3:0] IS = 0; // Init state counter
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/* Synchronize PHI2, RAS, CAS */
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always @(posedge RCLK) begin
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PHI2r <= PHI2; PHI2r2 <= PHI2r; PHI2r3 <= PHI2r2;
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RASr <= !nCRAS; RASr2 <= RASr; RASr3 <= RASr2;
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CASr <= !nCCAS; CASr2 <= CASr; CASr3 <= CASr2;
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end
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/* Latch 65816 bank when PHI2 rises */
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always @(posedge PHI2) begin
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if (Ready) RA11 <= (Din[6] && !n8MEGEN) ^ XOR8MEG; // Set RA11
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else RA11 <= 1'b0; // Reserved in mode register
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Bank[7:0] <= Din[7:0]; // Latch bank
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end
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/* Latch bank address, row address, WE, and CAS when RAS falls */
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always @(negedge nCRAS) begin
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if (Ready) begin
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RBA[1:0] <= CROW[1:0];
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RowA[9:0] <= MAin[9:0];
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end else begin
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RBA[1:0] <= 2'b00; // Reserved in mode register
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RowA[9] <= 1'b1; // "1" for single write mode
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RowA[8] <= 1'b0; // Reserved
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RowA[7] <= 1'b0; // "0" for not test mode
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RowA[6:4] <= 3'b010; // "2" for CAS latency 2
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RowA[3] <= 1'b0; // "0" for sequential burst (not used)
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RowA[2:0] <= 3'b000; // "0" for burst length 1 (no burst)
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end
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FWEr <= !nFWE;
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CBR <= !nCCAS;
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end
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/* Latch write data when CAS falls */
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always @(negedge nCCAS) begin
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WRD[7:0] <= Din[7:0];
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end
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/* State counter from RAS */
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always @(posedge RCLK) begin
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if (!RASr2) S <= 0;
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else if (S==2'h3) S <= 2'h3;
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else S <= S+2'h1;
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end
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/* Init state counter */
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always @(posedge RCLK) begin
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// Wait ~4.178ms (at 62.5 MHz) before starting init sequence
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FS <= FS+18'h1;
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if (FS[17:10]==8'hFF) InitReady <= 1'b1;
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end
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/* SDRAM CKE */
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always @(posedge RCLK) begin
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// Only 1 LUT4 allowed for this function!
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RCKE <= ((RASr || RASr2) && RCKEEN) || (!RASr2 && RASr3);
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end
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/* SDRAM command */
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always @(posedge RCLK) begin
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if (Ready) begin
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if (S==0) begin
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if (RASr2) begin
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if (CBR) begin
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// AREF
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nRCS <= 1'b0;
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nRRAS <= 1'b0;
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nRCAS <= 1'b0;
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nRWE <= 1'b1;
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RA10 <= 1'b1; // RA10 is don't care
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end else begin
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// ACT
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nRCS <= 1'b0;
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nRRAS <= 1'b0;
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nRCAS <= 1'b1;
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nRWE <= 1'b1;
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RA10 <= 1'b1; // Bank RA10 consistently "1"
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end
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// Enable clock only for reads
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RCKEEN <= !CBR && !FWEr;
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end else if (RCKE) begin
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// PCall
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nRCS <= 1'b0;
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nRRAS <= 1'b0;
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nRCAS <= 1'b1;
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nRWE <= 1'b0;
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RA10 <= 1'b1; // "all"
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RCKEEN <= 1'b1;
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end else begin
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// NOP
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nRCS <= 1'b1;
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nRRAS <= 1'b1;
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nRCAS <= 1'b1;
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nRWE <= 1'b1;
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RA10 <= 1'b1; // RA10 is don't care
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RCKEEN <= 1'b1;
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end
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nRowColSel <= 1'b0; // Select registered row addres
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end else if (S==1) begin
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// NOP
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nRCS <= 1'b1;
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nRRAS <= 1'b1;
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nRCAS <= 1'b1;
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nRWE <= 1'b1;
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RA10 <= 1'b1; // RA10 is don't care
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nRowColSel <= 1'b1; // Select asynchronous column address
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RCKEEN <= !CBR; // Disable clock if refresh cycle
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end else if (S==2) begin
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if (!FWEr && !CBR) begin
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// RD
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nRCS <= 1'b0;
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nRRAS <= 1'b1;
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nRCAS <= 1'b0;
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nRWE <= 1'b1;
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RA10 <= 1'b1; // Auto-precharge
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end else begin
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// NOP
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nRCS <= 1'b1;
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nRRAS <= 1'b1;
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nRCAS <= 1'b1;
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nRWE <= 1'b1;
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RA10 <= 1'b1; // RA10 is don't care
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end
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nRowColSel <= 1'b1; // Select asynchronous column address
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RCKEEN <= !CBR && FWEr; // Enable clock only for writes
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end else if (S==3) begin
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if (CASr2 && !CASr3 && !CBR && FWEr) begin
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// WR
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nRCS <= 1'b0;
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nRRAS <= 1'b1;
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nRCAS <= 1'b0;
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nRWE <= 1'b0;
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RA10 <= 1'b1; // Auto-precharge
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end else begin
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// NOP
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nRCS <= 1'b1;
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nRRAS <= 1'b1;
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nRCAS <= 1'b1;
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nRWE <= 1'b1;
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RA10 <= 1'b1; // RA10 is don't care
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end
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nRowColSel <= !(!FWEr || CASr3 || CBR);
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RCKEEN <= !(!FWEr || CASr2 || CBR);
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end
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end else if (InitReady) begin
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if (S==0 && RASr2) begin
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if (IS==0) begin
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// NOP
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nRCS <= 1'b1;
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nRRAS <= 1'b1;
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nRCAS <= 1'b1;
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nRWE <= 1'b1;
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RA10 <= 1'b1; // RA10 is don't care
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end else if (IS==1) begin
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// PC all
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nRCS <= 1'b0;
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nRRAS <= 1'b0;
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nRCAS <= 1'b1;
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nRWE <= 1'b0;
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RA10 <= 1'b1; // "all"
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end else if (IS==9) begin
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// Load mode register
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nRCS <= 1'b0;
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nRRAS <= 1'b0;
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nRCAS <= 1'b0;
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nRWE <= 1'b0;
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RA10 <= 1'b0; // Reserved in mode register
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end else begin
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// AREF
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nRCS <= 1'b0;
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nRRAS <= 1'b0;
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nRCAS <= 1'b0;
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nRWE <= 1'b1;
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RA10 <= 1'b1; // RA10 is don't care
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end
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IS <= IS+4'h1;
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end else begin
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// NOP
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nRCS <= 1'b1;
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nRRAS <= 1'b1;
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nRCAS <= 1'b1;
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nRWE <= 1'b1;
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RA10 <= 1'b1; // RA10 is don't care
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end
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if (S==3 && !RASr2 && IS==15) Ready <= 1'b1;
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nRowColSel <= 1'b0; // Select registered row address
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RCKEEN <= 1'b1;
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end else begin
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// NOP
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nRCS <= 1'b1;
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nRRAS <= 1'b1;
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nRCAS <= 1'b1;
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nRWE <= 1'b1;
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RA10 <= 1'b1; // RA10 is don't care
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nRowColSel <= 1'b0; // Select registered row address
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RCKEEN <= 1'b0;
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end
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end
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/* Submit command when PHI2 falls */
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always @(negedge PHI2) begin
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// Magic number check
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if (C1WR && Din[7:0]==8'hC1) begin // "C1" magic number
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if (ADSubmitted) begin
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CmdEnable <= 1'b1;
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end
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C1Submitted <= 1'b1;
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ADSubmitted <= 1'b0;
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end else if (ADWR && Din[7:0]==8'hAD) begin // "AD" magic number
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if (C1Submitted) begin
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CmdEnable <= 1'b1;
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end
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ADSubmitted <= 1'b1;
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C1Submitted <= 1'b0;
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end else if (C1WR || ADWR) begin // wrong magic number submitted
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CmdEnable <= 1'b0;
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C1Submitted <= 1'b0;
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ADSubmitted <= 1'b0;
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end else if (CMDWR) CmdEnable <= 1'b0;
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// Submit command
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if (CMDWR && CmdEnable) begin
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// if (Din[7:4]==4'h0 && Din[3:2]==2'b00) begin // MAX w/LED
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// if (Din[7:4]==4'h0) begin // MAX w/o LED
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if (Din[7:4]==4'h0 && Din[3:2]==2'b01) begin // LCMXO / iCE40 / AGM
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// if (Din[7:4]==4'h0 && Din[3:2]==2'b10) begin // LCMXO2
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XOR8MEG <= Din[0] && !(LEDEN && Din[1]);
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end else if (Din[7:4]==4'h0) begin // Unsupported type
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XOR8MEG <= 0;
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end else if (Din[7:4]==4'h1) begin
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CmdLEDEN <= Din[1];
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Cmdn8MEGEN <= !Din[0];
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CmdSubmitted <= 1'b1;
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end else if (Din[7:4]==4'h2) begin
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// Reserved for MAX commands
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end else if (Din[7:4]==4'h3 && !Din[3]) begin
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// SPI (LCMXO, iCE40, AGM) commands
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CmdLEDEN <= LEDEN;
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Cmdn8MEGEN <= n8MEGEN;
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CmdUFMCS <= Din[2];
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CmdUFMCLK <= Din[1];
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CmdUFMSDI <= Din[0];
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CmdSubmitted <= 1'b1;
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end else if (Din[7:4]==4'h3 && Din[3]) begin
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// Reserved for LCMXO2 commands
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// Din[1] - Shift when high, execute when low
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// Din[0] - Shift data
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end
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end
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end
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/* UFM Control */
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always @(posedge RCLK) begin
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if (!InitReady && FS[17:10]==8'h00) begin
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nUFMCS <= 1'b1;
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UFMCLK <= 1'b0;
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UFMSDI <= 1'b0;
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end else if (!InitReady && FS[17:10]==8'h01) begin
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nUFMCS <= 1'b0;
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UFMCLK <= 1'b0;
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UFMSDI <= 1'b0;
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end else if (!InitReady && FS[17:10]==8'h02) begin
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nUFMCS <= 1'b0;
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UFMCLK <= FS[4];
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case (FS[9:5]) // Shift out read data command (0x03)
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5'h00: UFMSDI <= 1'b0; // command bit 7 (0)
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5'h01: UFMSDI <= 1'b0; // command bit 6 (0)
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5'h02: UFMSDI <= 1'b0; // command bit 5 (0)
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5'h03: UFMSDI <= 1'b0; // command bit 4 (0)
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5'h04: UFMSDI <= 1'b0; // command bit 3 (0)
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5'h05: UFMSDI <= 1'b0; // command bit 2 (0)
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5'h06: UFMSDI <= 1'b1; // command bit 1 (1)
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5'h07: UFMSDI <= 1'b1; // command bit 0 (1)
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5'h08: UFMSDI <= 1'b0; // address bit 23 (0)
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5'h09: UFMSDI <= 1'b0; // address bit 22 (0)
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5'h0A: UFMSDI <= 1'b0; // address bit 21 (0)
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5'h0B: UFMSDI <= 1'b0; // address bit 20 (0)
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5'h0C: UFMSDI <= 1'b0; // address bit 19 (0)
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5'h0D: UFMSDI <= 1'b0; // address bit 18 (0)
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5'h0E: UFMSDI <= 1'b0; // address bit 17 (0)
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5'h0F: UFMSDI <= 1'b0; // address bit 16 (0)
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5'h10: UFMSDI <= 1'b0; // address bit 15 (0)
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5'h11: UFMSDI <= 1'b0; // address bit 14 (0)
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5'h12: UFMSDI <= 1'b0; // address bit 13 (0)
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5'h13: UFMSDI <= 1'b1; // address bit 12 (0)
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5'h14: UFMSDI <= 1'b0; // address bit 11 (0)
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5'h15: UFMSDI <= 1'b0; // address bit 10 (0)
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5'h16: UFMSDI <= 1'b0; // address bit 09 (0)
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5'h17: UFMSDI <= 1'b0; // address bit 08 (0)
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5'h18: UFMSDI <= 1'b0; // address bit 07 (0)
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5'h19: UFMSDI <= 1'b0; // address bit 06 (0)
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5'h1A: UFMSDI <= 1'b0; // address bit 05 (0)
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5'h1B: UFMSDI <= 1'b0; // address bit 04 (0)
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5'h1C: UFMSDI <= 1'b0; // address bit 03 (0)
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5'h1D: UFMSDI <= 1'b0; // address bit 02 (0)
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5'h1E: UFMSDI <= 1'b0; // address bit 01 (0)
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5'h1F: UFMSDI <= 1'b0; // address bit 00 (0)
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endcase
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end else if (!InitReady && FS[17:10]==8'h03) begin
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nUFMCS <= 1'b0;
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UFMCLK <= FS[4];
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UFMSDI <= 1'b0;
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// Latch n8MEGEN and LEDEN
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if (FS[9:5]==5'h00 && FS[4:0]==5'h10) n8MEGEN <= !UFMSDO;
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if (FS[9:5]==5'h01 && FS[4:0]==5'h10) LEDEN <= !UFMSDO;
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end else if (!InitReady && FS[17:10]!=8'hFE && FS[17:10]!=8'hFF) begin
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nUFMCS <= 1'b0;
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UFMCLK <= FS[1];
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UFMSDI <= 1'b0;
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end else if (!InitReady) begin
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nUFMCS <= 1'b1;
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UFMCLK <= 1'b0;
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UFMSDI <= 1'b0;
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end else if (!PHI2r2 && PHI2r3 && CmdSubmitted) begin
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// Set user command signals after PHI2 falls
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LEDEN <= CmdLEDEN;
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n8MEGEN <= Cmdn8MEGEN;
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nUFMCS <= !CmdUFMCS;
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UFMCLK <= CmdUFMCLK;
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UFMSDI <= CmdUFMSDI;
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end
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end
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endmodule
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