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- `timescale 1 ns / 1 ns
- //////////////////////////////////////////////////////////////////////////////////
- // Company: Rehkopf
- // Engineer: Rehkopf
- //
- // Create Date: 01:13:46 05/09/2009
- // Design Name:
- // Module Name: address
- // Project Name:
- // Target Devices:
- // Tool versions:
- // Description: Address logic w/ SaveRAM masking
- //
- // Dependencies:
- //
- // Revision:
- // Revision 0.02 - All new combinatorial glory. fucking slow.
- // Additional Comments:
- //
- //////////////////////////////////////////////////////////////////////////////////
- module address(
- input CLK,
- input [2:0] MAPPER, // AVR detected mapper
- input [23:0] SNES_ADDR, // requested address from SNES
- input SNES_CS, // "CART" pin from SNES (active low)
- output [19:0] SRAM_ADDR, // Address to request from SRAM
- output [3:0] ROM_SEL, // which SRAM unit to access (active low)
- input AVR_ENA, // enable AVR master mode (active low)
- input MODE, // AVR(1) or SNES(0) ("bus phase")
- output IS_SAVERAM, // address/CS mapped as SRAM?
- output IS_ROM, // address mapped as ROM?
- input [23:0] AVR_ADDR, // allow address to be set externally
- input ADDR_WRITE,
- output SRAM_BHE,
- output SRAM_BLE,
- output SRAM_ADDR0
- );
- reg [22:0] SRAM_ADDR_BUF;
- reg [3:0] ROM_SEL_BUF;
- reg [3:0] AVR_ROM_SEL_BUF;
- reg [3:0] CS_ARRAY[3:0];
- reg [1:0] AVR_BANK;
- wire [3:0] CURRENT_ROM_SEL;
- wire [22:0] SRAM_ADDR_FULL;
- initial begin
- CS_ARRAY[0] = 4'b0001;
- CS_ARRAY[1] = 4'b0010;
- CS_ARRAY[2] = 4'b0100;
- CS_ARRAY[3] = 4'b1000;
- AVR_BANK = 2'b0;
- end
- /* currently supported mappers:
- Index Mapper
- 000 HiROM
- 001 LoROM
- */
- /* HiROM: SRAM @ Bank 0x20-0x3f, 0xa0-0xbf
- Offset 6000-7fff */
- assign IS_SAVERAM = ((MAPPER == 3'b000) ? (!SNES_ADDR[22]
- & SNES_ADDR[21]
- & &SNES_ADDR[14:13]
- & !SNES_ADDR[15]
- )
- /* LoROM: SRAM @ Bank 0x70-0x7f, 0xf0-0xff
- Offset 0000-7fff */
- :(MAPPER == 3'b001) ? (&SNES_ADDR[22:20]
- & (SNES_ADDR[19:16] < 4'b1110)
- & !SNES_ADDR[15]
- & !SNES_CS)
- : 1'b0);
- assign IS_ROM = ( (MAPPER == 3'b000) ? ( (!SNES_ADDR[22]
- & SNES_ADDR[15])
- |(SNES_ADDR[22]))
- : (MAPPER == 3'b001) ? ( (SNES_ADDR[15] & !SNES_ADDR[22])
- |(SNES_ADDR[22]) )
- : 1'b0);
-
- assign SRAM_ADDR_FULL = (MODE) ? AVR_ADDR
- : ((MAPPER == 3'b000) ?
- (IS_SAVERAM ? SNES_ADDR[14:0] - 15'h6000
- : SNES_ADDR[22:0])
- :(MAPPER == 3'b001) ?
- (IS_SAVERAM ? SNES_ADDR[14:0]
- : {1'b0, SNES_ADDR[22:16], SNES_ADDR[14:0]})
- : 21'b0);
- assign SRAM_BANK = SRAM_ADDR_FULL[22:21];
- assign SRAM_ADDR = SRAM_ADDR_FULL[20:1];
- // XXX assign ROM_SEL = (MODE) ? CS_ARRAY[AVR_BANK] : IS_SAVERAM ? 4'b1000 : CS_ARRAY[SRAM_BANK];
- assign ROM_SEL = 4'b0001;
- assign SRAM_BHE = !AVR_ENA ? SRAM_ADDR_FULL[0] : 1'b0;
- assign SRAM_BLE = !AVR_ENA ? !SRAM_ADDR_FULL[0] : 1'b0;
- assign SRAM_ADDR0 = SRAM_ADDR_FULL[0];
- endmodule
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