From cf62bb4ee147c5ab51ada2437ac876f627fbb542 Mon Sep 17 00:00:00 2001
From: FreeArtMan <dos21h@gmail.com>
Date: Sun, 14 Oct 2018 14:09:26 +0100
Subject: Initial cpu8 isa

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 cpu8_spec/ISA_CPU8_0_0_4.md | 155 ++++++++++++++++++++++++++++++++++++++++++++
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 create mode 100644 cpu8_spec/ISA_CPU8_0_0_4.md

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+# ISA
+
+## Intro
+create 8 bit risc cpu named CPU8, alldata is sended trought serail interface and read
+with io commands
+
+## Goals
+
+create cpu description for 8 bit mini cpu
+
+# Architecrure overveiw
+## RAM
+RAM size 64k(minimal addressable amount 2/4bytes? TBD), should be enought for most operations
+register amount TBD, as much as possible?
+
+## CPU
+CPU supports simple command executions, data for registers are transsfered
+from internal RAM.
+Supports simple IRQ of operatio  results
+
+# Command set
+
+Command size 16bit(maybe change to 32bits?)
+will be enought to handle alot of registers, and vectors, anc crc and stuff), data size is 8bit
+Commands are in format
+
+CMD REG, MEM
+CMD REG, PARAM
+CMD REG, REG
+CMD MEM, REG
+
+# Command types
+## Arithmetical
+### Addition
+__ADD reg, reg__
+__INC reg__
+### Substraction
+__SUB reg, reg__
+__DEC__
+### Multiplication
+__MUL reg, reg__
+### Division
+__DIV reg, reg__
+
+### Modulo
+__MOD reg, reg__
+
+### Reverse
+__NEG reg__
+
+### Bitwise OR
+__OR REG, REG__
+
+### Bitwise AND
+__AND REG, REG__
+
+### Bitwise XOR
+__XOR REG, REG__
+
+### Compare
+Equal
+__CMPE REG, REG__
+above
+__CMPA REG, REG__
+belove
+__CMPB REG, REG__
+equal or above
+__CMPEA REG, REG__
+equal or belove
+__CMPEB REG, REG__
+Not equal
+__CMPNE REG, REG__
+### Jump
+program treated like RO written to memory, not possible to modify from programm itself
+__JMP STEP__
+
+
+### Set values to register
+__SET REG, VAL__
+__SET REG, MEM__
+
+
+## Memory manipulations
+### SETZEROS
+__SETZ reg__
+SETZ mem
+
+### SET TO VALUE
+__SETV reg, [8bit]__
+SETV mem, [8bit]
+
+## IO manipulation
+### Get value from port
+__INB reg, port__
+### Set value to prot
+__OUTB port, reg__
+### Input port state
+__INSTATE reg, port__
+### Output port state
+__OUTSTATE port, reg__
+### Port type
+__PORTT port__
+check what kind of device is at that port
+
+## State manipulation
+### Read IO statu register
+__SIO reg__
+
+## Interrupt managment
+### Rise intrrupt
+__INT num__
+    rise interrupt
+### Interrupt handling
+#### Disable interrupt
+__INTD num__
+#### Enable interrupt
+__INTE num__
+
+
+# Interfaces to outer worlds
+
+Serial interface, from CPU point of view, writting writes byte to port,
+further thats is translated to port
+
+Supported interfaces could be I2C, SPI, I2S, 1wite, trought FPGA
+that could connect some real world stuff, like terminal or any
+otherkind of device. 
+
+# Interrupt handler
+Interrupt handlder recieve interrupt, get address from interrupt table and jump
+according to address in interrupt table.
+
+
+## Interrupt type
+### Arithmetic error
+### Memory error
+### Hardware error
+### User defined interrupts
+User can define or map any kind of event to interrupt, and when its happends then
+interrupt workout where to jump in a codespace.
+
+# Implementation plan
+Steps to do finish projects
+
+Create
+  Initial block diagramm
+  Assembler
+  Disassembler
+  Block diagramm
+  Some programs for real world
+  Implementation in FPGA?
+    More step to describe
+  Real world example usage, calc temperature from sensor
+  
+  
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