|
The 74HC373 are similar to the kind of chips I used in my 8051 school project but it was a couple octal D flip-flops instead of latches because we really don't need the two inputs, set and reset, and it took less board space (less pins). Maybe 74HC574 or similar but I don't really remember. Maybe there are chips for 16bit now.
The 8051 I used is similar to the CDP1802 you are using. It had 16bit addresses multiplexed in 8bit and 8bit data without multiplexing. It had no type of memory management. Only supported instructions to read/write registry or external address with the first block of external addresses taken by the internal memory.
I do remember that I expanded the address from 16bit to 32bit and the data I used both 8bit and 32bit. The drive I used had a 32bit block mode that read 8bit at a time in burst.
Expanding the data bus, from the hardware point of view, is identical to expanding the address bus with just one difference. The data bus is bidirectional so you need flip-flops (or latches) facing each direction of communication, they need to have an high impedance output when not enabled and care must be taken to select the correct facing flip-flops.
That is basically what is shown in the link you posted. However, the circuit I used was a little simpler but used more wires. The circuit in the link appears to "shift-register" the data from the two 74HC574 via the 74HC245 to the CPU.
In my circuit I just had all 74HC574 connected to the bus and just enabled the one I wanted to read/write. I had that "chip enabling" automated by using an extra shift-register that would shift a single one and was reset at the beginning of every read/write. And disabled the write chips by negating the read/write pin.
Like you said, is just more reads or writes from the CPU perspective. But still faster than parallel port and way faster than the serial port I had to use in the project that followed.
1MB? That's luxury
It's almost as much RAM as my favourite laptop has (compaq contura aero 4/25 with 4MB)
|
|
|
|
|
ElectronProgrammer wrote: The circuit in the link appears to "shift-register" the data from the two 74HC574 via the 74HC245 to the CPU.
Nah, it's just decoding two IO ports and generating the signals when to enable the outputs of the latches and the
ElectronProgrammer wrote: 1MB? That's luxury This is just the second prototype. The 'real' one will have up to 16 Mb and up to 8 processors.
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.
|
|
|
|
|
Are you documenting your project anywhere public? I'd be interested in following your progress.
|
|
|
|
|
I saw Bob's outfit and realized today must be something special. Looking it up on line I discovered July 1st celebrates the founding of the Chinese Communist Party[^] and thus, in celebration, he put on a lot of made-in-China garments!
Well - I'm glad that's settled.
Ravings en masse^ |
---|
"The difference between genius and stupidity is that genius has its limits." - Albert Einstein | "If you are searching for perfection in others, then you seek disappointment. If you seek perfection in yourself, then you will find failure." - Balboos HaGadol Mar 2010 |
|
|
|
|
|
|
Balboos was making a funny.
Social Media - A platform that makes it easier for the crazies to find each other.
Everyone is born right handed. Only the strongest overcome it.
Fight for left-handed rights and hand equality.
|
|
|
|
|
ZurdoDev wrote: Balboos was making a funny.
And it looks like it was made in China, because Slacker is still waiting for it to be delivered!
|
|
|
|
|
放屁
Ravings en masse^ |
---|
"The difference between genius and stupidity is that genius has its limits." - Albert Einstein | "If you are searching for perfection in others, then you seek disappointment. If you seek perfection in yourself, then you will find failure." - Balboos HaGadol Mar 2010 |
|
|
|
|
|
Hey! Not in polite company...
|
|
|
|
|
dandy72 wrote: in polite company... That's where you get the most BANG for the buck.
Ravings en masse^ |
---|
"The difference between genius and stupidity is that genius has its limits." - Albert Einstein | "If you are searching for perfection in others, then you seek disappointment. If you seek perfection in yourself, then you will find failure." - Balboos HaGadol Mar 2010 |
|
|
|
|
|
Social Media - A platform that makes it easier for the crazies to find each other.
Everyone is born right handed. Only the strongest overcome it.
Fight for left-handed rights and hand equality.
|
|
|
|
|
Nice.
|
|
|
|
|
Sorry, I forgot to laugh.
|
|
|
|
|
Well today is also National Joke Day, so you've hit a 2-in-1 there!
Tomorrow is World UFO Day, so I wonder if Bob will dress up like an alien to celebrate it?
|
|
|
|
|
musefan wrote: Tomorrow is World UFO Day, so I wonder if Bob will dress up like an alien to celebrate it? How many of our lounge posters will take the day off to celebrate (their national holiday?)
Ravings en masse^ |
---|
"The difference between genius and stupidity is that genius has its limits." - Albert Einstein | "If you are searching for perfection in others, then you seek disappointment. If you seek perfection in yourself, then you will find failure." - Balboos HaGadol Mar 2010 |
|
|
|
|
|
W∴ Balboos, GHB wrote: How many of our lounge posters will take the day off to celebrate (their national holiday?)
Not sure, allow me to escalate your query back to mothership and I will get back to you.
*music starts playing*
please hold... your domination is important to us.
|
|
|
|
|
Celt used around selection (8)
"We can't stop here - this is bat country" - Hunter S Thompson - RIP
|
|
|
|
|
Another rather old word!
"I have no idea what I did, but I'm taking full credit for it." - ThisOldTony
AntiTwitter: @DalekDave is now a follower!
|
|
|
|
|
I thought CCC is English only - the youngsters does not know Latin...
"The only place where Success comes before Work is in the dictionary." Vidal Sassoon, 1928 - 2012
|
|
|
|
|
A lot of English is derived from Latin.
And from French, German, Old Norse, Greek, Dutch, and a bunch of others that we have adopted over the years ...
"I have no idea what I did, but I'm taking full credit for it." - ThisOldTony
AntiTwitter: @DalekDave is now a follower!
|
|
|
|
|
Yes, but wonder if native English speakers do know this specific, without some classic background (I knew it because they forced me to learn Latin as kid )...
"The only place where Success comes before Work is in the dictionary." Vidal Sassoon, 1928 - 2012
|
|
|
|
|
They tried to teach me it as well, but most of it just bounced off.
"I have no idea what I did, but I'm taking full credit for it." - ThisOldTony
AntiTwitter: @DalekDave is now a follower!
|
|
|
|
|
|
I would like to thank the other gentlemen for their useful hints.
We don't want another one of these tomorrow, so
DELECTUS
|
|
|
|
|
Latin is the mother of lots of languages - and you solved it so you are up tomorrow - it was an easy clue though despite the Latin part
"We can't stop here - this is bat country" - Hunter S Thompson - RIP
|
|
|
|