6502.org Forum  Projects  Code  Documents  Tools  Forum
It is currently Tue Nov 12, 2024 3:30 pm

All times are UTC




Post new topic Reply to topic  [ 6 posts ] 
Author Message
 Post subject: 1mhz Crystal
PostPosted: Tue Apr 12, 2011 7:12 pm 
Offline

Joined: Tue Apr 12, 2011 7:08 pm
Posts: 20
Location: NB, Canada
I am new to this and am trying to build my first project. I bought some chips from Jameco, But I made a mistake and bought a 2mhz crystal and it looks like 2 of the chips(6522, 6551) are only 1mhz. I cant seem to find a 1mhz crystal for less then $30 dollers. I have seen some projects using the 4 pin "cans" others say no, you need to use the 2 pin and build the clock.

So, can you use a 4 pin crystal, or do I need to keep looking for a 2 pin?
and Does anybody know if a good place in Canada to buy these parts, shipping rom the U.S.A gets a bit high after duty.


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Tue Apr 12, 2011 7:51 pm 
Offline
User avatar

Joined: Fri Dec 11, 2009 3:50 pm
Posts: 3367
Location: Ontario, Canada
The 4-pin can will be OK; just make sure it's rated for a 5 volt supply. (I think some of them use 3.3V instead.) The 4-pin can is a complete oscillator. Unlike a crystal, it requires a power supply but does not need external circuitry to produce the output you require.

You haven't said what CPU you're using -- is it a 6502 or a 'C02, for instance?

Another option for you is to build an oscillator using the 2 Mhz crystal, then use a 74HC74 or similar flip-flop to divide the 2 Mhz down to 1 Mhz.

Sayal Electronics is a Canadian supplier you should investigate. As for US companies, DigiKey is also good. They manage all the customs red tape, so that part of it is completely transparent. You only end up paying the $8 for shipping.

Cheers,

Jeff


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Tue Apr 12, 2011 8:34 pm 
Offline
User avatar

Joined: Fri Aug 30, 2002 1:09 am
Posts: 8539
Location: Southern California
Quote:
Another option for you is to build an oscillator using the 2 Mhz crystal, then use a 74HC74 or similar flip-flop to divide the 2 Mhz down to 1 Mhz.

The oscillator in the can is the easiest, neatest solution, but if you can't get down to 1MHz, then start with 2MHz or 4MHz and use the clock divider circuit that's in most 6502 manufacturers' data sheets to get down to 1MHz. It uses a flip-flop IC.


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Tue Apr 12, 2011 11:45 pm 
Offline

Joined: Tue Apr 12, 2011 7:08 pm
Posts: 20
Location: NB, Canada
Thanks for the help

It is the R6502a
https://www.jameco.com/webapp/wcs/stores/servlet/OrderDetail?storeId=10001&catalogId=10001&langId=-1&orderId=15446509&close=1

I looked at the data sheet and did not see anything about a clock divider

the shipping was only $8 so II also ordered a http://search.digikey.com/scripts/DkSearch/dksus.dll?lang=en&site=US&WT.z_homepage_link=hp_go_button&KeyWords=X937-ND%09&x=28&y=8

Any recommendation on a good basic OSCILLOSCOPE with a good price


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Wed Apr 13, 2011 3:21 am 
Offline
User avatar

Joined: Fri Aug 30, 2002 1:09 am
Posts: 8539
Location: Southern California
Since you ordered a 1MHz oscillator can, you won't need the divider, but here it is in text for future reference. Run the oscillator's output to the clock input of one section of a 74xx74 dual flip-flop, then connect its Q\ output to its D input, and you'll have half the frequency at the Q output to feed to the processor. The SET\ and CLR\ inputs to the flip-flop should be pulled up. Since there are two sections of this in a 74xx74, you can put one after the other to divide by four if you want to. Each section will divide by two and give you a symmetrical output.

I have not looked on eBay, but any ol' 20MHz dual-trace oscilloscope should do for what you want (as long as it works and has a good set of x10 probes with it). There ought to be a lot of them out there on the used market.


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Wed Apr 13, 2011 4:09 am 
Offline
User avatar

Joined: Thu May 28, 2009 9:46 pm
Posts: 8482
Location: Midwestern USA
GARTHWILSON wrote:
Run the oscillator's output to the clock input of one section of a 74xx74 dual flip-flop...

74AC74 or 74ABT74 are your best choices, as they produce single digit nanosecond rise and fall times.

_________________
x86?  We ain't got no x86.  We don't NEED no stinking x86!


Top
 Profile  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 6 posts ] 

All times are UTC


Who is online

Users browsing this forum: No registered users and 15 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: