18F87J10 Question

cfernandez · Joined: 18 Oct 2003 Posts: 145

Hi,

Somebody use the 18F87J10??, is really compatible with the 18F8722 ??

Please tell me your experience.

thank you very much!

Best Regards,

iso9001 · Joined: 02 Dec 2003 Posts: 262

Never used either but I beleive that since the J10 is Standard Flash it can not selfwrite/bootload. I may be mistaken on that, thought I remember reading that somewhere.

Aside from EEPROM and flash type, some of the IO pins are different, the 22 looks to have more alternate uses for some pins.

If you are going to run an external clock your fine, but the 22 has the faster internal clock.

The J10 has a max voltage of 3.6 and 22 is 5.5, the 22 also has 2 pins for power, so pin compatibility is unlikely.

Large price difference.

Plus 50 other differences.

Asking if they are compatible is really useless since no one knows what you are DOING with them..... Lots of things are compatible as long as you place limits on how they are used.

JBM · Joined: 12 May 2004 Posts: 54 Location: edinburgh, Scotland

I've had a little bit of experience with the the 18F67J10, the little brother (same series though) as the 18F87J10.

One thing to be VERY careful about is the ENVREG pin - this denotes whether you want to supply an external core voltage (a max of 2.5V is allowed). Related to this is that one of the Vdd pins on the 18F8722 is not necessarily a Vdd pin on the J10 - there has to be a 10uF capacitor on the line, or the external core voltage. The datasheet explains it in deital.

Almost all of the pinouts are the same, but not all - a very important difference!
-JBM

cfernandez · Joined: 18 Oct 2003 Posts: 145

Dear ISO9001

You say that with J10 not have bootload????????, This is the most important point for me. Can you confirm this?

Thank you very much!!

Ttelmah · Guest

The J10, can write it's own memory. This is the only 'feature' required, to allow a bootloader to work. The thing that can make it 'difficult', is that the memory erases in 1024 byte blocks. Hence you cannot have a small bootloader occupying just the bottom 256 bytes for example, but must leave the entire 1024 bytes at the base of memory unchanged. Also the code protection, treats the entire internal memory space as a single block, making it impossible to protect the bootloader...
So it can be made to support a bootloader, but is not the nicest chip to do it on.

Best Wishes

iso9001 · Joined: 02 Dec 2003 Posts: 262

Thats what it was.

The 'standard flash' description on the microchip website is a little ambiguous.