This is a THCO-MIPS 16bits CPU implemented in Verilog, served as the course project in Computer Organization (2013Fall) in Tsinghua University.
Authors:
- ppwwyyxx (ppwwyyxxc@gmail.com)
- Ray Song (emacsray@gmail.com)
- Vury Leo (i@vuryleo.com)
On reset process, the PC register will be set to FF00, where it BIOS located.
R0 ~ R7 ==> "0000" ~ "0111" IH ==> "1000" SP ==> "1001" RA ==> "1010"
0000 ~ 7FFF physical memory, so only 31KB of memory is available 8000 ~ 8AFF graphic memory FE00 keyboard input FF00 ~ FFFF rom
On debug mode, VGA will display the status of CPU as a supervising program for convenient debuging. The left part will be the registers storage, the right part will be the result cache of each step. So, developers will spot which part was going wrong very easily. Though it spend lots of compiling time and lots of logic gate, it is effective in most situations.
In order to support hardware interrupt, an extra instruction is introduced.
It is called eret. And its binary format is 1000000000000000, and hexadecimal format is 8000.
When executing this instruction, CPU will clear the interrupt signal and reset PC to EPC that stored when interrupt occers.
Notice eret instruction is NOT a jump instruction, so a delay slot isn't appear.
naiveKernel is a basic OS kernel that implements serval system calls, and is embedded a text editor and a interpreter.
0000 ~ 0003 boot instruction Just a b instruction that point to real program 0004 ~ 003f interrupt vector table 0400 I/O buffer start 7FFE stack bottom
0 -> reserved 1 -> load keyboard input into I/O buffer 2 -> read I/O buffer 3 -> write to graphic memory
For interrupts' detail, please refer to wiki.
MIT