Forums

crystal selection

Started by Bob White October 8, 2003
I'm using an MC68HC911B32. All of a sudden I'm getting occasional Clock
Monitor Fail interrupts. The crystal and processor both seem a little warm.
I've noticed in the past that manufacturers don't use the same language that
Motorola does in describing the type of crystal that should be used.

I used 24pF to ground at each xtal lead and 10MOhm between leads. I can
find no Motorola requirements for the Xtal or the caps in my "Advance
Information" book. I have no idea why I chose 24pF.

Does anyone have a manufacturer and part number for a crystal (8 MHz) that
is a good match? Or even a manufacturer and type? Surface mount only need
apply.

Thanks,
Bob White



We use a Raltron Part #AS-4.000-18-SMD-STD-T on 9S12 boards. I believe
it is available at higher frequencies.
22pF caps to ground and 330kOhm across the crystal complete the circuit.
The same part is used on eval boards from Future Electronics.

Regards,
Kevin Antony I'm using an MC68HC911B32. All of a sudden I'm getting occasional Clock
Monitor Fail interrupts. The crystal and processor both seem a little
warm.
I've noticed in the past that manufacturers don't use the same language
that
Motorola does in describing the type of crystal that should be used.

I used 24pF to ground at each xtal lead and 10MOhm between leads. I can
find no Motorola requirements for the Xtal or the caps in my "Advance
Information" book. I have no idea why I chose 24pF.

Does anyone have a manufacturer and part number for a crystal (8 MHz)
that
is a good match? Or even a manufacturer and type? Surface mount only
need
apply.

Thanks,
Bob White

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554205:HM/A95053/R=0/SIG4gf29oe/*http:/ashnin.com/clk/muryutaitake
nattogyo?YH707890&yhad95053> Click Here! <http://us.adserver.yahoo.com/l?M$4522.3707890.4968055.1261774/D=egrou
pmail/S=:HM/A95053/rand19925516>

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At 10:58 AM 10/8/2003 -0700, you wrote:
>I'm using an MC68HC911B32. All of a sudden I'm getting occasional Clock
>Monitor Fail interrupts.
>I used 24pF to ground at each xtal lead and 10MOhm between leads. I can
>find no Motorola requirements for the Xtal or the caps in my "Advance
>Information" book. I have no idea why I chose 24pF.
>
>Does anyone have a manufacturer and part number for a crystal (8 MHz) that
>is a good match? Or even a manufacturer and type?

Last board I did with the B32 had an ECS ECS-160-20-5PDN crystal (16 MHz,
surface mount). That's Digikey XC694CT-ND. If you want to go down to 8
MHz it should be on the same page in the catalog.

The 911B32 had a very robust oscillator (not low power, but very reliable).
I've NEVER had any clock problems, even with some fairly poor layouts.

jmk
-----------
James M. Knox
TriSoft ph 512-385-0316
1109-A Shady Lane fax 512-366-4331
Austin, Tx 78721
-----------


ERROR - I can't believe I did it. I'm using an MC68HC912B32, not HC11. So
I'm hoping that the HC912 has as robust an oscillator as the '11 did. I
never had a problem with the '11 either.

Thanks,
Bob White

----- Original Message -----
From: "James M. Knox" <>
To: <>
Sent: Wednesday, October 08, 2003 11:41 AM
Subject: Re: [68HC12] crystal selection At 10:58 AM 10/8/2003 -0700, you wrote:
>I'm using an MC68HC911B32. All of a sudden I'm getting occasional Clock
>Monitor Fail interrupts.
>I used 24pF to ground at each xtal lead and 10MOhm between leads. I can
>find no Motorola requirements for the Xtal or the caps in my "Advance
>Information" book. I have no idea why I chose 24pF.
>
>Does anyone have a manufacturer and part number for a crystal (8 MHz) that
>is a good match? Or even a manufacturer and type?

Last board I did with the B32 had an ECS ECS-160-20-5PDN crystal (16 MHz,
surface mount). That's Digikey XC694CT-ND. If you want to go down to 8
MHz it should be on the same page in the catalog.

The 911B32 had a very robust oscillator (not low power, but very reliable).
I've NEVER had any clock problems, even with some fairly poor layouts.

jmk
-----------
James M. Knox
TriSoft ph 512-385-0316
1109-A Shady Lane fax 512-366-4331
Austin, Tx 78721
-----------
--------------------
">http://docs.yahoo.com/info/terms/