|
I'm talking to you, @raddevus! Did you have to write these articles[^] and wake up sleeping dogs? Why did you have to make me think of building something again?
I'm done with the schematics for my 8 bit computer. This is the plan:
Board 1:
- CPU and clock (around 5 MHz)
- BIOS ROM 16k
- Fixed RAM (for the stack) 8k
- Complete selection logic for ROM, RAM and up to 16 memory mapped devices
- Interrupt handling logic, including a register showing the pending interrupts.
Board 2 (and 3 if needed):
- DIY PS/2 port for the keyboard (quite experimental)
- DIY PS/2 port for the mouse (just as experimental)
- RS232 port, baud rate generated from the system clock. This is plan B if the PS/2 ports make trouble.
- Parallel port
- System Timer (mostly to provide the timing for multitasking)
- DIY IDE port based on a Intel 80C55 port.
- Up to two (master/slave) IDE devices with up to 128 GB, probably simple SD cards with an IDE adapter. SSDs for 8 bit computers  Implementing a compact but adequate file system will be some work.
- Interface for a 128 x 64 pixel LCD display
Board 3:
A paged memory with up to 256 pages mapped onto a 16 k block = 4mb total (if I find enough room on the board).
Board 4:
A second paged memory, identical to the first, but jumpered to use a second 16k block.
Board 5:
- MC6847 Video generator
- 8k graphics memory
- Sound chip (perhaps a C64's SID or one of the many Yamaha sound chips, not sure yet)
Next step: Dusting off the breadboards and build a prototype.
I have lived with several Zen masters - all of them were cats.
His last invention was an evil Lasagna. It didn't kill anyone, and it actually tasted pretty good.
|
|
|
|
|
This all sounds like a very cool project and I am humbled that reading my articles motivated you to start work on that. Hope you will write up your work as you go along. It would be really interesting.
My research and writing was motivated by reading two great books that I always talk about:
1. Code: The Hidden Language of Computer HW & SW by Charles Petzold[^]
2. AVR Programming: Learning to Write Software for Hardware (Elliot Williams)[^]
I've always been interested in OS and how it boots itself. I've always wanted something extremley small and simple to learn about it, but don't find much. That has become a very distant goal : to write an extremely small OS-type of thing for an Arduino -- an interface to the hardware ops.
I'm just moving so slowly with my writing that it'll take me forever.
Hope to hear more about your great and inspiring projects. 
|
|
|
|
|
Look at the case I want to put it in, if my 3D printer is up to the task: Star Trek TOS Tricorder[^]
I have lived with several Zen masters - all of them were cats.
His last invention was an evil Lasagna. It didn't kill anyone, and it actually tasted pretty good.
|
|
|
|
|
That is very cool. I hope you get that worked out.
|
|
|
|
|
PS/2 keyboard - use a PIC as an inteface chip: PS2 Keyboard to serial converter[^] - that way you take the load of the processor (since KB data is clocked) and can just hand your computer the "scan codes". Same connector shoudl work for mouse as well.
(And there are little 8 pin PIC chips that you can just use an R/C network as the OSC which should do it with an absolute minimum of other circuitry.)
Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...
AntiTwitter: @DalekDave is now a follower!
|
|
|
|
|
I thought about that, but there is one small problem. The PIC does not have tristate outputs to the data bus. I would still have to add some additional logic to get this to work.
Instead I use shift registers with integrated latches and tristate outputs. Two of these plus four more standard 74HCXXX logic ICs are enough for both ports and a logic to latch the bits and fire an interrupt when a byte has been clocked in. The CPU then only has to read from the right latch to get the byte and push it into a buffer.
Those six ICs will be the very first thing I will put onto a breadboard and test.
I have lived with several Zen masters - all of them were cats.
His last invention was an evil Lasagna. It didn't kill anyone, and it actually tasted pretty good.
|
|
|
|
|
CodeWraith wrote: The PIC does not have tristate outputs to the data bus.
Just configure the ports as inputs and switch to output mode when needed:
bsf TRISx,b ; input / tri-state at power on
bsf/bcf PORTx,b ; latch data
bcf TRISx,b ; data output
delay ; or use a timer interrupt
bsf TRISx,b ; back to tri-state
|
|
|
|
|
Good to know. That makes using PICs plan B if plan A fails and using a terminal with RS232 becomes plan C.
I have lived with several Zen masters - all of them were cats.
His last invention was an evil Lasagna. It didn't kill anyone, and it actually tasted pretty good.
|
|
|
|
|
OriginalGriff wrote: And there are little 8 pin PIC chips that you can just use an R/C network as the OSC which should do it with an absolute minimum of other circuitry.
There are even PICs with internal oscillators that did not requiry any external components (besides the usual capacitor(s) on the power supply line).
|
|
|
|
|
noob confused with OG's posts in QA (4)
|
|
|
|
|
C R A P?
Just a guess, given my posts are involved... 
Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...
AntiTwitter: @DalekDave is now a follower!
|
|
|
|
|
I'm so tempted to say Bono here.
This space for rent
|
|
|
|
|
I'm guessing you are right: The Lounge[^]
Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...
AntiTwitter: @DalekDave is now a follower!
|
|
|
|
|
He could also be going Michael Elphick on us.
This space for rent
|
|
|
|
|
|
OK, how about "OBON"?
Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...
AntiTwitter: @DalekDave is now a follower!
|
|
|
|
|
Is there only one more option?
|
|
|
|
|
Well, we could always go with Nobo 
This space for rent
|
|
|
|
|
Looks like I'm coming back Monday then...
|
|
|
|
|
Well, it's a bank holiday and I certainly don't want to be doing it.
This space for rent
|
|
|
|
|
And I'm mentioned in the clue, so I don't want to either!
Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...
AntiTwitter: @DalekDave is now a follower!
|
|
|
|
|
Nah, there are loads:
NOOB
NOBO
NBOO
ONOB
ONBO
OBNO
OOBN
OONB
OBON
BONO
BNOO
But I'm sure I'm missing something...
Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...
AntiTwitter: @DalekDave is now a follower!
|
|
|
|
|
Boon?
cheers,
Super
------------------------------------------
Too much of good is bad,mix some evil in it
|
|
|
|
|
|
For this entire thread, it is not permitted to reuse the same word twice (Subject line and signatures excluded)
Your turn!
Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...
AntiTwitter: @DalekDave is now a follower!
|
|
|
|
General 
News 
Suggestion 
Question 
Bug 
Answer 
Joke 
Praise 
Rant 
Admin 
Submit an article or tip
