::SHE+ILA::'s Microsequencer Redrawn [$16]

More about ::SHE+ILA::'s Microsequencer Redrawn [$16]

Well, here's a better diagram of ::SHE+ILA::'s Microsequencer. The Microstate register (at the left) contains a 16bit address, corresponding to the microstep number in the Writable Control Store (which is confusingly marked <u>STATE</u>) at the very top of the disgram, and should be marked "WCS". It consists of 64K of static RAM, and contains the microinstructions which define the operation of the ::SHE+ILA:: Instruction Set. The output of this WCS is latched by the Microcommand Register (marked "LINK"), whose outputs control tha ALUOP inputs of the Arithmetic Logic Unit (74LS181), and also the Bus Control Unit (not shown), and also feeds back to the STATE register, which determines the next microstep in the current machine-code instruction. The WCS is bootstrapped from the host machine (Apple ][ or Pentium PC) via a bidirectional tri-state buffer which is interfaced to "LINK". Yay :)