'HC908JL Clock Source

[BobMac]

Hi Everybody and Happy NOT Monday!
I've got a little head scratcher here and sure could use a word of encouragement. I have been using the 908JL08 for a while and with good success.
I convinced the boss that a bit more Flash would be GOOD... he bought it ;o). The sample chips I just got want to run on the internal clock at 50Kc or there abouts and pay no attention to the outboard 9.8Mc Crystal. how can we get this thing to run with the external crystal clock?

Help would be greatly appreciated.
Best regards, Bob and the Guys

[rhinoceroshead]

What is it doing?  How are you getting the 50kHz measurement?  Are you successfully programming the device?

If so, then my guess is that it is working, but the COP is timing out.  The reason I say this is because the internal RC oscillator - that is, the one that has no external parts - will not run the CPU.  It runs the COP only.  The only clocks that can drive the CPU are either the crystal oscillator or the RC oscillator that uses an external resistor and capacitor.  Since they are brand new chips, the FLASH should be all 1s, and the crystal clock should be selected by default - unless you are writing the clock select bit to a zero while programming.  But if that were the case then it shouldn't work without an external resistor and capacitor - and it would be impossible to have both the RC and crystal connected since they use the same pin.

[BobMac]

Hi Rhino...

 The chips powered up and could not be communicated with using our programming adapter. I scoped the ocsillator pin (OSC2) to make sure that it was working and found that instead of the external crystal running the show I was observing 50Kc square waves.

 This crystal has been running a few other 908JL8 chips so I know it is good. I agree, the flash should be all 1s and hence the external crystal osc. selected. Something is screwy here.   

 Since we can not communicate with the chips, we can not program them and inadvertaintly errase the oscillator select bit in the (MOR).

 This would indicate to me that these devices are dead by some means unknown.

I'll get a couple more from another batch and try them out.

Bob    

[RockyRoad]

Bob -

I know that it's not Monday, but it feels like it... I'm confused about what part you're trying to get working now and what part you've been using successfully.

I assume that you're porting your code from the old part to the new. That might help figuring out what's going on.

- Rocky

[BobMac]

Hi Rocky.

 The chips we were using are the 908jl8 and the ones I want to switch to are the 908jl16. I cant even get the JL16 to communicate yet but I do get 50KHz on the (OSC2) pin. Bad!

Bob

[RockyRoad]

Bob -

I don't see why you can't at least get into monitor mode to program the JL16 when you've been programming the JL8 ok in the same setup.

I don't have any JL16's handy to try it out. I've ordered some samples, but I don't know when they'll show up.

In the meantime, what tool are you using to try to program the parts?

- Rocky