The devices were originally profiled as 40MHz but the released silicon is
stated at 25MHz. I am lead to believe (off the record), the problem with the
speed is the TABLE commands which are used for data arrays or for
re-programming the device
live (boot loader stuff).

If this function is not used, you may be able to run it faster but Microchip
of course will not guarantee anything out of there spec sheets of course. EG
I wouldn't risk it for a production device.

The speed restriction is a fault with the flash memory design apparently,
the following same family devices are going to be 40MHz (the 8520 is a true
40MHz part) and eventually (no time scale) there will be an A revision which
will run at 40MHz and let the TABLE commands function.

Hope this helps,

Graham



-----Original Message-----
From: pic microcontroller discussion list
[mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Bob Ammerman
Sent: 02 May 2003 00:06
To: PICLIST@MITVMA.MIT.EDU
Subject: Re: [PIC] 18Fxx20 DEVICE frequencies


They were originally announced as 40MHz parts, but mChip found they didn't
work well at that speed. An errata was released reducing the max clock speed
to 25MHz. One can hope mChip will eventually fix the problem and create a
version of the silicon without the errata.

Bob Ammerman
RAm Systems

----- Original Message -----
From: "James Williams" <williams.engineering@VERIZON.NET>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Thursday, May 01, 2003 6:59 PM
Subject: [PIC] 18Fxx20 DEVICE frequencies


> Hello,
>
> Does anyone know why the 18Fxx20, in particular, the ones that are
> currently available to the public, devices have a max frequency of
> 25MHz?  For some reason, DigiKey shows that they can operate at 40MHz,
> but Microchips' site says only 25MHz.
>
> Regards,
>
>
>
> James
>
>
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