pixy
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Author: noulmao

Forked from: noulmao/pixy

Project access type: Public

Description:

pixy


pixy is a simple 32-bit processor with twelve instructions.

pixy can...

here are the instructions:

  • add <rn>, <rs | value>
  • sub <rn>, <rs | value>
  • and <rn>, <rs>
  • or <rn>, <rs>
  • xor <rn>, <rs>
  • not <rn>
  • b <value>
  • mov <rn>, <rs | value>
  • load <rn>, [<rs>]
  • sto <rs | value>, [<rn>]
  • test <rn>, <rs>
  • stop

arrangement:

  1. top left: clock in
  2. middle left: data in
  3. bottom left: input enable
  4. top right: address out
  5. middle right: data out
  6. bottom right: output enable

connecting to pixy:

  • pick a device you'll be using to store programs and data, i.e. RAM.
  • link data in to RAM's data output through a tristate.
  • link data out to RAM's data input through a tristate.
  • link address out to RAM's address input.
  • link clock in to an oscillator. 
  • link input and output enables to the tristates.

when the clock starts, the processor will try to execute any instructions found at address 0x0000.


internals:

  • the CU uses microcode stored in an EEPROM to implement the instruction set.
  • information is transferred between components using a data bus which is wrapped around the circuit.
  • programs can access four general purpose registers and RAM. They can also talk to any peripherals connected via memory mapping.
  • a FIN signal is used to mark the end of an instruction and save clock cycles.
  • conditional instructions work by triggering FIN (or not) based on ALU flags.

Created: Aug 28, 2021

Updated: Aug 28, 2021

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