6502.org Forum Projects Code Documents Tools Forum
It is currently Sun Nov 24, 2024 7:31 am

View unanswered posts | View active topics


Board index » 6502.org Users Forum » Hardware

All times are UTC




Post new topic Reply to topic  Page 2 of 2
  [ 21 posts ]  Go to page Previous  1, 2
  Previous topic | Next topic 
Author Message
GARTHWILSON
PostPosted: Thu Aug 05, 2021 9:27 am 
Offline
User avatar

Joined: Fri Aug 30, 2002 1:09 am
Posts: 8546
Location: Southern California
MichaelM wrote:
The PIC is naturally a 4 clock cycle machine. Running Phi2 into the clock input of the PIC is going to effectively force the PIC to operate at 1/4 the clock frequency of the 6502/65C02.

The PIC16's instruction cycle is 4 clock cycles.  The 65c02 also averages approximately 4 cycles per instruction, a little more or a little less depending on what you're doing; so they would be approximately equal except that the 65c02's richer instruction set lets it get the job done in about half as many instructions, according to my experience.  (I've brought a dozen products to market with PIC16's, but never used its PSP.)  A PIC16 running at 20MHz would not be less than half the speed of a 65c02 running at 20MHz.

_________________
http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?
Top
 Profile  
Reply with quote  
BigEd
PostPosted: Thu Aug 05, 2021 10:06 am 
Offline
User avatar

Joined: Thu Dec 11, 2008 1:28 pm
Posts: 10986
Location: England
But I'd still agree with Michael: the PIC should be clocked fast. Especially for the difficult case, where a read request comes in and the PIC needs to do some work to get the right value into the output port before the end of the read cycle.

I do see hints that some PIC18F models have a PSP but haven't found a simple answer. It does seem that the PIC18Fs to hand lack the PSP.
Top
 Profile  
Reply with quote  
Jmstein7
PostPosted: Thu Aug 05, 2021 2:01 pm 
Offline

Joined: Sun May 30, 2021 2:16 am
Posts: 375
BigEd wrote:
But I'd still agree with Michael: the PIC should be clocked fast. Especially for the difficult case, where a read request comes in and the PIC needs to do some work to get the right value into the output port before the end of the read cycle.

I do see hints that some PIC18F models have a PSP but haven't found a simple answer. It does seem that the PIC18Fs to hand lack the PSP.


PSP seems to be a "hidden feature" in a bunch of 18Fs, though I could easily be mistaken. They seem to have that capability, but it is not mentioned in the datasheet.

Again, I could be wrong.

-Jon
Top
 Profile  
Reply with quote  
Jmstein7
PostPosted: Fri Aug 06, 2021 1:56 pm 
Offline

Joined: Sun May 30, 2021 2:16 am
Posts: 375
MichaelM wrote:
I too haven't used the PSP in a way more years than I'd like to remember.

I do wonder about connecting the PIC's clock input to the Phi2 clock of the 6502/65C02.


Michael,

Ditto, I had the same though - so, maybe I can use the PIC clock to drive PHI2? I'm using a WDC65c02S, so it can handle a little speed. Or, maybe I can drive the PIC at a "high speed" and send a 1/4 clock to PHI2?

-Jon
Top
 Profile  
Reply with quote  
GARTHWILSON
PostPosted: Fri Aug 06, 2021 7:22 pm 
Offline
User avatar

Joined: Fri Aug 30, 2002 1:09 am
Posts: 8546
Location: Southern California
They can both handle 20MHz, and probably more, but I've never heard of any efforts to see how much more the PIC can handle above what it is spec'ed for.  It sounds like there's more margin on the '02 than there is on the PIC.  In any case, make sure you give the '02 a really clean clock signal with fast slew rates.

_________________
http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?
Top
 Profile  
Reply with quote  
Jmstein7
PostPosted: Fri Aug 06, 2021 7:31 pm 
Offline

Joined: Sun May 30, 2021 2:16 am
Posts: 375
GARTHWILSON wrote:
They can both handle 20MHz, and probably more, but I've never heard of any efforts to see how much more the PIC can handle above what it is spec'ed for. It sounds like there's more margin on the '02 than there is on the PIC. In any case, make sure you give the '02 a really clean clock signal with fast slew rates.


Yeah. I’m going to have to use a good ‘scope for this one. I’ve suffered the plight of crappy signals too many times. Lots of wasted boards.

-Jon

PS thanks for the soldering tips; I’m fairly good at that now. I almost never use breadboards for anything but really basic tests, now.
Top
 Profile  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  Page 2 of 2
  [ 21 posts ]  Go to page Previous  1, 2

Board index » 6502.org Users Forum » Hardware

All times are UTC


Who is online

Users browsing this forum: No registered users and 48 guests

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
6502.org is an ongoing project by Mike Naberezny and contributors.