32khz PLL to IMO - chicken and egg problem

A catchall for PSoC Mixed-Signal Array (microcontroller) discussions not captured by the other forums.

Moderator: ericb

32khz PLL to IMO - chicken and egg problem

Postby Mr_E » Tue Jan 21, 2014 8:28 am

I have a temperature compensated 32khz external clock that I would like to use to generate an accurate 24Mhz IMO. I see how to connect (pin 13) the clock to my processor (CY8C29466), but I also noticed that one of the debugger/programmer pins connects to this same processor pin.

Won't the external 32Khz signal destroy the ability for me to debug/program the chip soldered on the circuit board? If so, how is one supposed to use an external crystal with PSOC1 devices?
User avatar
Mr_E
The Big Cheese
The Big Cheese
 
Posts: 297
Joined: Wed Aug 11, 2004 7:08 am
Website: http://www.microframecorp.com
Location: Oklahoma, USA

Re: 32khz PLL to IMO - chicken and egg problem

Postby Mr_E » Tue Jan 21, 2014 8:48 am

Upon further reading, I'm not sure what I want can be done. PLL is done with an external CRYSTAL. I have a 32khz clock source.

There is a separate input (P1.4) for an external clock source, but then I need to feed in 24Mhz directly, which I don't have. Sigh.
User avatar
Mr_E
The Big Cheese
The Big Cheese
 
Posts: 297
Joined: Wed Aug 11, 2004 7:08 am
Website: http://www.microframecorp.com
Location: Oklahoma, USA

Re: 32khz PLL to IMO - chicken and egg problem

Postby bobmarlowe » Tue Jan 21, 2014 1:10 pm

There are no debug capabilities for a PSoC1 except when using the ICE-Cube. So after programming the chip via ISSP a 32kHz crystal will work again.
Sorry, there is no chicken today.


Bob
User avatar
bobmarlowe
The Big Cheese
The Big Cheese
 
Posts: 1490
Joined: Thu Oct 06, 2011 2:03 am
Location: Germany

Re: 32khz PLL to IMO - chicken and egg problem

Postby dseguine » Tue Jan 21, 2014 4:51 pm

Mr E:
You can't debug while using an external 32 kHz oscillator input, but you can use that input for normal operation.
There are a few tricks, some of which may be in app notes, but here goes:
1. Set up a resistive bias point 0.7 V below Vdd, connect this to the crystal input on P1.1.
2. Connect series resistor and capacitor from your external source, set resistor value to limit the level to 0.7Vpp.
3. Start chip with oscillator set to internal.
4. Boot in the normal manner with ILO and IMO.
5. Allow for settling time in your external oscillator.
6. Switch (in code) low speed oscillator from internal ILO to crystal.
7. Switch (in code) main oscillator from internal IMO to PLL mode.
you should now be working as you requested.
---- Dennis
dseguine
Cheese Wheel
Cheese Wheel
 
Posts: 70
Joined: Wed Jan 19, 2005 12:21 pm
Website: http://www.cypress.com
Location: Seattle


Return to “%s” PSoC1 General

Who is online

Users browsing this forum: Bing [Bot] and 4 guests