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Simple MicroProcessor Architecture - Tiny 8 bit CPU
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Simple MicroProcessor Architecture

SMPA CPU v0.1 - Open Source 8bit CPU concept by Nikita Lindmann


Registers 1-6 is common use registers AR-FR
7-12'th registers are reserved
13 and 14'th registers (IPTR and SEGR) are used for addressation
15 is FLAGS register
Zero register is special register for each function's result(LASTR)


Full byte address is SEGR*255+IPTR, limited by 65536 bytes or 64 kbyte.
First 6400 bytes reserved for BIOS and Memory mapped IO(means it's readonly).


Register-register commands:

0000'0000 0000'0000
\_______/ \__/ \__/
 Opcode   Registers

Valie commands:

0000'0000 0000'0000
\_______/ \_______/
 Opcode     Value


0x00 - nop - Do nothing

Memory and register operations
0x01 - rmem Reg, Reg - Load data from memory at Reg:Reg(page:offset) to LASTR
0x02 - wmem Reg, Reg - Store data from LASTR to memory at Reg:Reg(page:offset)
0x03 - mv Reg Reg - Copy data from first register to second, LASTR not changes
0x04 - rev Reg - Copy data from register to LASTR

Math and logic

0x05 - add Reg, Reg - Add integer value from first register to second
0x06 - or Reg, Reg - Bit OR logic function
0x07 - and Reg, Reg - Bit AND logic function
0x08 - not Reg - Logical inversion


0x09 - jmp Reg, Reg - Jump to Reg:Reg(page:offset)
0x0A - eq Reg, Reg - If data in both registers is equal, next command will be passed
0x0B - less Reg, Reg
0x0C - more Reg, Reg
0x0D - leq Reg, Reg
0x0E - meq Reg, Reg
0x0F - neq Reg, Reg

Direct data load

0x10 - setAR Value - Load Value to register AR
0x11 - setBR Value
0x12 - setCR Value
0x13 - setDR Value
0x14 - setER Value
0x15 - setFR Value
0x16 - setFLAGR Value

Stack operations

0x17 - ls Reg - Load data from top of stack to LASTR
0x18 - ss Reg - Save data from reg to top of stack


0x19 - int Value - Generate interruption


00 Does nothing 01 Halts the cpu 02 Send single character from LASTR onto screen.
03 Read singe character from buffer to LASTR.

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