MC68376

[philip_vuong]

We have used the MC68376 for replacement of the MC68336 in our product.  But there are two CAN pins (pin1-CANTX0 and pin160-CANRX0) on the MC68376 will not be used for our purposes but need to know how to terminate them (either tied high or low or something-else).  We don’t just want to leave them floating.  Any suggestions?

[TomE]

The Transmit pin is an output. You don't need to do anything with that.

I agree with the OP that the receive pin shouldn't be left floating. If you don't enable the controller it doesn't care about the pin state, so pull up or down doesn't matter. I'd use a resistor rather than a direct short to ground or power though.

Tom

[Hui_Ma]

Hi,

Since MC68376 and Mc68336 has the same internal CPU32 Core, the instruction set between this two are the same, means the fetch and execute codes are basically the same if the program it is the same.
Also check this note *NOTE: MC68336 REVISION D AND LATER (F60K AND LATER MASK SETS) HAVE ASSIGNED PINS 1 AND 160 AS “NO CONNECT”, TO ALLOW PIN COMPATIBILITY WITH THE MC68376. FOR REVISION C (D65J MASK SET) DEVICES, PIN 1 IS VSS AND PIN 160 IS VDD.

So, customer can left MC68376 pin1-CANTX0 and pin160-CANRX0 floating.

best regards,

Mike

[philip_vuong]

Hi Mike,

Can we tie the two pins (Pin 1 and Pin160) together (short to each other) ?

If not, what is the reason?

thanks

philip

[Hui_Ma]

Hi Philip,

From the MC68376 user manual, the CANRX0 pin is input and CANTX0 pin is output during reset and after reset.

There with below Note to avoid input direction pin floating, which could add system power consumption:

Based on this note, we would recommend to pull up/down CANRX0 pin with 10Kohm resistor & CANTX0 pin is output direction can left floating.

Yes, you can tie two pins (pin 1 and pin160) together with a 10Kohm resistor to VSS/VDD (with disabled TouCAN module).

best regards,

Mike

[philip_vuong]

Hi Mike,

Thanks for your response. Tie the two pins (pin 1 and pin160) together with a 10Kohm resistor to VSS/VDD is only to avoid power consumption.  But we are more concerned about the whole microcontroller function properly if we tie these two pins together.  Any affect for proper microcontroller function?

philip

[Hui_Ma]

Hi Philip,

Tie the two pins (pin1 and pin160) together doesn't affect MC68376 functions, which looks like TouCAN module works in loop back mode.

While, that design will bring big potential risk.

I just imagine a scenario that if the board replace MC68376 chip with previous MC68336 chip one day, especially FOR REVISION C (D65J MASK SET). It connects the chip VSS and VDD together. 

So, if possible, I would not recommend to tie two pins (pin1 and pin160) together, handle two pins separately with external pull down/up resistors. Thanks.

best regards,

Mike

[philip_vuong]

Hi Mike,

Thanks for your response. Tie the two pins (pin 1 and pin160) together with a 10Kohm resistor to VSS/VDD is only to avoid power consumption. But we are more concerned about the whole microcontroller function properly if we tie these two pins together. Any affect for proper microcontroller function?

philip