Multiphase clock

Multiphase clock

Dec

29

2009

I have found an interesting bug in my design that opened my eyes to one important aspect. The problem is related to the memory chips’ /WE (write enable) signal which should be asserted when I want to store data in memory. With nearly every TTL device in my design being synchronous, altering their states on ...
read more →

Design · Design - control · Design - memory

Gate-level simulator

Gate-level simulator

Dec

22

2009

The simulator is ready and running first simulations of my CPU, proving for the first time that the envisioned mesh of wires and chips may actually work. Writing the simulator was not easy, but I think it was a great exercise. Not using Verilog for this purpose was not a bad idea at all. The ...
read more →

Simulation

Microcode pre-release

Nov

29

2009

I decided to stop at this point and declare the initial version of the microcode complete (although the machine has not been simulated yet and the microcode is still untested). I have not yet completed faults and interrupts microcode, because I don’t know how I am going to do user/supervisor mode context switching and which ...
read more →

Design - control

Bitwise shifts – here comes the shifter

Bitwise shifts – here comes the shifter

Nov

27

2009

I have added yet another component to the high level design. It is a shifter and its role is to… shift. More specifically, it is a right shifter which will allow me to perform bitwise right shift in just one clock cycle. Until now, the design was lacking this ability. Doing left shifts is fairly ...
read more →

Design - ALU

Architecture update

Architecture update

Nov

17

2009

At a certain point when microcoding I realized that my architecture was obviously wrong in one aspect. Frankly speaking it was so wrong that I am embarrassed I had not noticed this earlier. The problem was that all address registers were connected to the 8-bit data bus. With such layout, every address loading operation consumed ...
read more →

Design

New toys

New toys

Nov

15

2009

I have been collecting various stuff I will need to build the computer for some time already. As I am still struggling to complete the microcode assembler (I keep changing my mind on various microcode word structures back and forth), I decided to take a little brake and share photos of what I have gathered. ...
read more →

General