RE: MPC555, TouCAN

I've never tried that before, but it sounds like it should work fine.  If you make the TX pins CMOS push/pull, you don't need the pull-ups.  PU's only required if you make the tx pins open drain and in that case, 3.3K is close to the limit if you want to test upto 1M baud, you could reduce that value slightly.

For testing (assuming I don't have transceivers on my board), I will often connect all the 4 pins together (put a 100ohm between the two TX's just to be safe) with a 1K or 2K pull up and configure the TX pins for open drain mode. This works the same as your AND gate and can be used if you don't have the spare gate on your board.

Regards,
Allan

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of [email protected]
Sent: Tuesday, June 21, 2005 9:21 AM
To: [email protected]
Subject: [MPC500] MPC555, TouCAN


I am attempting to develop a test for the MPC555 TouCAN.  
The two ports are connected (externally) to each other 
using a quad 74HCT08 AND gate and 3.3k-ohm pull-up resistors.

CAN_A_RX = CAN_B_RX = CAN_A_TX AND CAN_B_TX

Are there any problems with this concept 
(assuming software configuration is correct)?

I don't see anything in the UM, the MPC500 Embedded 
Learning Tutorial, or the MPC500 QuickStart about 
communicating between A and B (everything is "A or B").

Thanks.

Brian Lawry
Mfg Software Engineer
Compressor Controls Corp
[email protected]


[Non-text portions of this message have been removed]



-----------------------------------------------------------
To learn more about Freescale Microcontrollers, please visit http://www.freescale.com/mcu


 
Yahoo! Groups Links



 



-----------------------------------------------------------
To learn more about Freescale Microcontrollers, please visit
http://www.freescale.com/mcu


 
Yahoo! Groups Links

<*> To visit your group on the web, go to:
    http://groups.yahoo.com/group/MPC500/

<*> To unsubscribe from this group, send an email to:
    [email protected]

<*> Your use of Yahoo! Groups is subject to:
    http://docs.yahoo.com/info/terms/