自制CPU（四）程序编写

在我们设计出来前边三种CPU之后，我们来进行程序的编写。

所谓程序的编写，就是；利用我们写好的CPU，根据我们可执行的指令集，来编写一段程序，可一直用我们的CPU来完成。

首先，我们在写程序之前，确定你的CPU可以执行load，store，beq，jump，add几种基础指令，如果这几个都没有，那这个程序怕是也做不出来的。

在你希望实现的小系统中，一定有你的外围电路，它是将你外部输入的数据写入外存/数据存储器 中的，并将运算结果读出并显示或... 之后你的指令在开始时寄存器堆中可以预先有操作数，也可以通过指令读入。程序在开始前进行load将数据从数据存储器中读入寄存器堆中，最后再从寄存器堆中用store写会到数据寄存器中。在运算中有判断时就使用beq来完成，直接跳转一般都在beq跳转到的位置进行有效操作完的下一条指令，为了实现如C语言中的if语句。

最终你的指令是写成一个case语句中或者写成一个.coe文件的，coe文件直接写入数据存储器中，

例如

?? ???? 32'd0 : instruction <= 32'b000001_00001_00100_0000000000000000;?? ??? ??? ?//1 1 4 000 lw
?? ??? ?32'd1 : instruction <= 32'b000000_00000_00001_00010_00000_000000;?? ??? ?//0 0 1 2 0 0 add
?? ??? ?32'd2 : instruction <= 32'b000001_00010_00101_0000000000000000;?? ??? ??? ?//1 2 5 000 lw
?? ??? ?32'd3 : instruction <= 32'b000000_00000_00010_00011_00000_000000;?? ??? ?//0 0 2 3 0 0 add
?? ??? ?32'd4 : instruction <= 32'b000001_00011_00110_0000000000000000;?? ??? ??? ?//1 3 6 000 lw
?? ??? ?32'd5 : instruction <= 32'b000000_00011_00010_01101_00000_000001;?? ??? ?//0 3 2 13 0 13 sub
?? ??? ?
?? ??? ?32'd6 : instruction <= 32'b000101_00110_01101_0000000000000001;?? ??? ??? ?//5 6 13 6 beq
?? ??? ?32'd7 : instruction <= 32'b000111_00000000000000000000000000;?? ??? ??? ??? ?//7 0 j ?
?? ??? ?32'd8 : instruction <= 32'b000101_00110_01101_0000000000000110;?? ??? ??? ?//5 6 13 6 beq
?? ??? ?32'd9 : instruction <= 32'b000000_00000_00111_01000_00000_000000;?? ??? ?//0 0 7 8 0 0 add
?? ??? ?32'd10 : instruction <= 32'b000000_00000_01000_01001_00000_000000;?? ??? ?//0 0 8 9 0 0 add
?? ??? ?32'd11 : instruction <= 32'b000000_00000_01001_01010_00000_000000;?? ??? ?//0 0 9 10 0 0 add
?? ??? ?32'd12 : instruction <= 32'b000000_00000_01010_01011_00000_000000;?? ??? ?//0 0 10 11 0 0 add
?? ??? ?
?? ??? ?32'd13 : instruction <= 32'b000101_00110_01101_0000000000000110;?? ??? ??? ?//5 6 13 6 beq
?? ??? ?32'd14 : instruction <= 32'b000101_00110_00010_0000000000000111;?? ??? ??? ?//5 6 2 7 beq
?? ??? ?32'd15 : instruction <= 32'b000101_00110_00011_0000000000001000;?? ??? ??? ?//5 6 3 8 beq
?? ??? ?32'd16 : instruction <= 32'b000101_00110_00111_0000000000001001;?? ??? ??? ?//5 6 7 9 beq
?? ??? ?32'd17 : instruction <= 32'b000101_00110_01000_0000000000001010;?? ??? ??? ?//5 6 8 10 beq
?? ??? ?32'd18 : instruction <= 32'b000101_00110_01001_0000000000001010;?? ??? ??? ?//5 6 9 10 beq
?? ??? ?32'd19 : instruction <= 32'b000101_00110_01010_0000000000001010;?? ??? ??? ?//5 6 10 10 beq
?? ??? ?
?? ??? ?32'd20 : instruction <= 32'b000000_00100_00101_01100_00000_000000;?? ??? ?//0 4 5 12 0 0 add
?? ??? ?32'd21 : instruction <= 32'b000111_00000000000000000000011110;????????? //7 30 j
?? ??? ?32'd22 : instruction <= 32'b000000_00100_00101_01100_00000_000001;?? ??? ?//0 4 5 12 0 1 sub
?? ??? ?32'd23 : instruction <= 32'b000111_00000000000000000000011110;??? x????? //7 30 j
?? ??? ?32'd24 : instruction <= 32'b000000_00100_00101_01100_00000_000010;?? ??? ?//0 4 5 12 0 2 and
?? ??? ?32'd25 : instruction <= 32'b000111_00000000000000000000011110;????????? //7 30 j
?? ??? ?32'd26 : instruction <= 32'b000000_00100_00101_01100_00000_000011;?? ??? ?//0 4 5 12 0 3 or
?? ??? ?32'd27 : instruction <= 32'b000111_00000000000000000000011110;????????? //7 30 j
?? ??? ?32'd28 : instruction <= 32'b000000_00100_00101_01100_00000_000100;?? ??? ?//0 4 5 12 0 4 nor
?? ??? ?32'd29 : instruction <= 32'b000111_00000000000000000000011110;????????? //7 30 j
?? ??? ?
?? ??? ?32'd30 : instruction <= 32'b000010_00000_01100_0000000000000000;?? ??? ??? ?//2 0 13 000 sw

?? ??? ?32'd31 : instruction <= 32'b000111_00000000000000000000000000;?? ??? ??? ??? ?//7 0 j? */

或者.coe文件

memory_initialization_radix =? 2 ;
memory_initialization_vector =
10001000001000100000000000000010,
00010100001000100000000000000010,
00001000000000000000000000000000,
10001000001000110000000000000000,
00010100011000100000000000000010,
10101100001001000000000100000010,
00001000000000000000000000000000,
10101100001001010000000100000010,

00001000000000000000000000000000,

最终烧录验证就实现了用CPU跑一个小程序了。

<iframe id="iframe_tags" data-elecfans_trackid="article_detail" data-tag='fpga' src="/static/iframe/course.html" width="100%" height="170" style="border: none;margin: 20px 0;"></iframe>