Block diagram

Block diagram

Nov

1

2009

As I am working through the microcode (and the microcode assembler) this finally required me to sketch a block diagram of the entire machine and the CPUs internal datapaths. The microcode is not ready yet (I have completed about 20 most typical instructions), neither is the assembler (I am adding features to the lexer and parser ...
read more →

Design

Sequencer tweaks

Sequencer tweaks

Oct

19

2009

When I started writing first microcode and sketching the overall block diagram I decided to tweak the microcode sequencer again a little. Here’s what has changed. Fetch. The 9-bit base address points to two 256-element pages. Addresses in page 00h-FFh store instructions directly visible to programmer, whereas page 100h-1FFh is reserved for pseudo-instructions which are ...
read more →

Design - control

Hewlett-Packard 1631D

Hewlett-Packard 1631D

Oct

16

2009

My 1631D logic analyzer and digitizing oscilloscope arrived yesterday. I bought it on US eBay a few weeks ago for as little as $70 (plus $40 shipping to Poland). The thing scared me at first with all the cables, buttons and… its size – it takes one third of my desk! Also, my wife looked ...
read more →

General

On microcode sequencing again. Final?

On microcode sequencing again. Final?

Oct

15

2009

I’ve changed my mind on microcode sequencing. Again. Ok, I know I would be fired if all this was for real, but I don’t like the sequencer design with ‘next’ field embedded in the microcode word anymore. The problem is with the ‘next’ field itself which I planned to be longer that 8 bits. This requires not ...
read more →

Design - control

HP hex displays – cosmic?

HP hex displays - cosmic?

Oct

3

2009

I bought some HP 4N54 hexadecimal displays some time ago at a surplus store. I plugged them into my breadboard just to check them and they all worked fine so I will use them as my debug displays when I start construction. This device fits the purpose very well for a couple of reasons. First ...
read more →

General

More on microcode sequencing

More on microcode sequencing

Sep

30

2009

It’s been a long time since I last posted on this site or did anything related to the project. Way too long. My paying job has had me extremely busy lately. Add to this a long awaited apartment flip we had, sooner than expected due to our contractor’s change of schedules and you’ve got the story. I ...
read more →

Design - control