// pi_buf.v v1 Frank Berndt
// pi buffer wrapper;
// :set tabstop=4

module pi_buf (
	clk, csb, addr, dih, dil, web, doh, dol
);

`include "define.vh"

	input clk;			// sync clock;
	input csb;			// chip enable;
	input [7:0] addr;	// address;
	input [40:0] dih;	// high write data;
	input [40:0] dil;	// low write data;
	input [1:0] web;	// write enables;
	output [40:0] doh;	// high read data;
	output [40:0] dol;	// low read data;

	// 256x82 sync SRAM, write enable granularity is 41;

`ifdef	NEC_PIBUF

	WBSRAMSHS256W41C3 pibuf0 (
		.DO40(dol[40]),
		.DO39(dol[39]),
		.DO38(dol[38]),
		.DO37(dol[37]),
		.DO36(dol[36]),
		.DO35(dol[35]),
		.DO34(dol[34]),
		.DO33(dol[33]),
		.DO32(dol[32]),
		.DO31(dol[31]),
		.DO30(dol[30]),
		.DO29(dol[29]),
		.DO28(dol[28]),
		.DO27(dol[27]),
		.DO26(dol[26]),
		.DO25(dol[25]),
		.DO24(dol[24]),
		.DO23(dol[23]),
		.DO22(dol[22]),
		.DO21(dol[21]),
		.DO20(dol[20]),
		.DO19(dol[19]),
		.DO18(dol[18]),
		.DO17(dol[17]),
		.DO16(dol[16]),
		.DO15(dol[15]),
		.DO14(dol[14]),
		.DO13(dol[13]),
		.DO12(dol[12]),
		.DO11(dol[11]),
		.DO10(dol[10]),
		.DO9(dol[9]),
		.DO8(dol[8]),
		.DO7(dol[7]),
		.DO6(dol[6]),
		.DO5(dol[5]),
		.DO4(dol[4]),
		.DO3(dol[3]),
		.DO2(dol[2]),
		.DO1(dol[1]),
		.DO0(dol[0]),
		.DI40(dil[40]),
		.DI39(dil[39]),
		.DI38(dil[38]),
		.DI37(dil[37]),
		.DI36(dil[36]),
		.DI35(dil[35]),
		.DI34(dil[34]),
		.DI33(dil[33]),
		.DI32(dil[32]),
		.DI31(dil[31]),
		.DI30(dil[30]),
		.DI29(dil[29]),
		.DI28(dil[28]),
		.DI27(dil[27]),
		.DI26(dil[26]),
		.DI25(dil[25]),
		.DI24(dil[24]),
		.DI23(dil[23]),
		.DI22(dil[22]),
		.DI21(dil[21]),
		.DI20(dil[20]),
		.DI19(dil[19]),
		.DI18(dil[18]),
		.DI17(dil[17]),
		.DI16(dil[16]),
		.DI15(dil[15]),
		.DI14(dil[14]),
		.DI13(dil[13]),
		.DI12(dil[12]),
		.DI11(dil[11]),
		.DI10(dil[10]),
		.DI9(dil[9]),
		.DI8(dil[8]),
		.DI7(dil[7]),
		.DI6(dil[6]),
		.DI5(dil[5]),
		.DI4(dil[4]),
		.DI3(dil[3]),
		.DI2(dil[2]),
		.DI1(dil[1]),
		.DI0(dil[0]),
		.A7(addr[7]),
		.A6(addr[6]),
		.A5(addr[5]),
		.A4(addr[4]),
		.A3(addr[3]),
		.A2(addr[2]),
		.A1(addr[1]),
		.A0(addr[0]),
		.WEB(web[0]),
		.CSB(csb),
		.BE(clk),
		.TBE(1'b0),
		.TEST(1'b0),
		.BUB(1'b1)
	);

	WBSRAMSHS256W41C3 pibuf1 (
		.DO40(doh[40]),
		.DO39(doh[39]),
		.DO38(doh[38]),
		.DO37(doh[37]),
		.DO36(doh[36]),
		.DO35(doh[35]),
		.DO34(doh[34]),
		.DO33(doh[33]),
		.DO32(doh[32]),
		.DO31(doh[31]),
		.DO30(doh[30]),
		.DO29(doh[29]),
		.DO28(doh[28]),
		.DO27(doh[27]),
		.DO26(doh[26]),
		.DO25(doh[25]),
		.DO24(doh[24]),
		.DO23(doh[23]),
		.DO22(doh[22]),
		.DO21(doh[21]),
		.DO20(doh[20]),
		.DO19(doh[19]),
		.DO18(doh[18]),
		.DO17(doh[17]),
		.DO16(doh[16]),
		.DO15(doh[15]),
		.DO14(doh[14]),
		.DO13(doh[13]),
		.DO12(doh[12]),
		.DO11(doh[11]),
		.DO10(doh[10]),
		.DO9(doh[9]),
		.DO8(doh[8]),
		.DO7(doh[7]),
		.DO6(doh[6]),
		.DO5(doh[5]),
		.DO4(doh[4]),
		.DO3(doh[3]),
		.DO2(doh[2]),
		.DO1(doh[1]),
		.DO0(doh[0]),
		.DI40(dih[40]),
		.DI39(dih[39]),
		.DI38(dih[38]),
		.DI37(dih[37]),
		.DI36(dih[36]),
		.DI35(dih[35]),
		.DI34(dih[34]),
		.DI33(dih[33]),
		.DI32(dih[32]),
		.DI31(dih[31]),
		.DI30(dih[30]),
		.DI29(dih[29]),
		.DI28(dih[28]),
		.DI27(dih[27]),
		.DI26(dih[26]),
		.DI25(dih[25]),
		.DI24(dih[24]),
		.DI23(dih[23]),
		.DI22(dih[22]),
		.DI21(dih[21]),
		.DI20(dih[20]),
		.DI19(dih[19]),
		.DI18(dih[18]),
		.DI17(dih[17]),
		.DI16(dih[16]),
		.DI15(dih[15]),
		.DI14(dih[14]),
		.DI13(dih[13]),
		.DI12(dih[12]),
		.DI11(dih[11]),
		.DI10(dih[10]),
		.DI9(dih[9]),
		.DI8(dih[8]),
		.DI7(dih[7]),
		.DI6(dih[6]),
		.DI5(dih[5]),
		.DI4(dih[4]),
		.DI3(dih[3]),
		.DI2(dih[2]),
		.DI1(dih[1]),
		.DI0(dih[0]),
		.A7(addr[7]),
		.A6(addr[6]),
		.A5(addr[5]),
		.A4(addr[4]),
		.A3(addr[3]),
		.A2(addr[2]),
		.A1(addr[1]),
		.A0(addr[0]),
		.WEB(web[1]),
		.CSB(csb),
		.BE(clk),
		.TBE(1'b0),
		.TEST(1'b0),
		.BUB(1'b1)
	);

`else	// NEC_PIBUF

	// behavioral buffer;
	// simulate no write-through;

	reg [40:0] pibufh [0:255];
	reg [40:0] pibufl [0:255];
	reg pibuf_en;
	reg [7:0] pibuf_a;
	reg [40:0] pibuf_dih;
	reg [40:0] pibuf_dil;
	reg [1:0] pibuf_we;

	always @(posedge clk)
	begin
		pibuf_en <= ~csb;
		pibuf_a <= addr;
		pibuf_dih <= dih;
		pibuf_dil <= dil;
		pibuf_we <= ~web;
		if(pibuf_en & pibuf_we[1])
			pibufh[pibuf_a] <= pibuf_dih;
		if(pibuf_en & pibuf_we[0])
			pibufl[pibuf_a] <= pibuf_dil;
	end

	assign doh = pibuf_en? pibufh[pibuf_a] : {41{1'bx}};
	assign dol = pibuf_en? pibufl[pibuf_a] : {41{1'bx}};

`endif	// NEC_PIBUF

endmodule