40x2 minimum circuit

[IronJungle]

Behold... I have a 40x2 that was given to me (lucky me!!!)

Looking at the documentation of my AXE091 Dev Board I see the min circuit for 28 pin devices, but not the 40x2.

A quick look seems to suggest they should be different due to the external resonator. Am I missing something?
Is there a document on the 40x2 min circuit? Is the external resonator required for all applications?

Thanks !

 

[westaust55]

The 28 and 40 pin X1 and X2 PICAXE parts do not need a resonator by default.
The resonator is only used when the SETFREQ command is used with a parameter &#8220;em<xx>&#8221; which selects the external responator.

For the minimum circuit, see PICAXE manual 1:http://www.picaxe.com/docs/picaxe_manual1.pdf
At page 35 there is the min cirucit for the 28 pin devices. Equally applicable for 40 pin parts (see page 42).
Note that by Note 3 under the scheamtic, the resonator is optional for all but some very early PICAXE chips. Same note exists on page 42 for 40 pin parts.

I believe the AXE091 has a resonator as much so folks can select an external resonator for higher accuracy an/or alternate clock speeds as desired for testing. It is not a mandatory component.

 

[srnet]

The 28X2 can be fitted with an external resonator too, but its not required for 28X2 or 40X2, unless you want to run faster than 16Mhz.

Both 28x2 and 40x2 have the same minimum circuit, different pin numbers though.

 

[westaust55]

Snap!

 

[IronJungle]

Great. Thanks, both of you. The different pins for the resonator on the 28 vs 40 was confusing me. That and the schematic in the AXE091 manual. I'm all set straight now (for now).

 

[Bill.b]

With the AXE091, the resonator is only connected to pins 13 and 14 of the 40 pin socket. it is not connected to any pin on the 28 pin socket.

If you are only using the 28 pin picaxe, be shaw to use the correct pins to connect any external connection. - the center set of pins marked 1 to 14.

Bill

 

[westaust55]

With the AXE091, the resonator is only connected to pins 13 and 14 of the 40 pin socket. it is not connected to any pin on the 28 pin socket.

If you are only using the 28 pin picaxe, be shaw to use the correct pins to connect any external connection. - the center set of pins marked 1 to 14.

Bill

@Bill,
How have you determined that the X1 resonator is not connected to the 28 Pin Chip connections?
You may well be right, but it is not what is shown on the AXE091 datasheet at page 3.
http://www.picaxe.com/docs/axe091.pdf

 

[westaust55]

Now home and had a look at my own AXE91 board.

Definitely traces (on the underside) from the resonator to the 40 pin outer header pins 13 an 14 then across to the 40 pin IC "socket", continuing (down the middle area of the 28 pin socket) to pins 9 and 10 on the 28 pin IC socket and then back out to pins 9 and 10 on the 28 pin "header" pins

Conclusion - the on-board resonator "X1" is connected to both the 28 pin and the 40 pin IC sockets