Emax

Hi, thank you for the test on your side. Here it still looks rather weird.
The problem is definietly related to the clock.

Let's make things as simple as possible. 

Let's detach everything from the Teensy, just get EMU's clock to the XCK (PD5) pin (besides VCC and GND) - but nothing else.

In this situation we've used an SN75176 line driver configured  as receiver like this:

CLK (from Emax:5)  ->  SN75176B:pin6 (A) 
SN75176B:pin7 (B) = L
SN75176B:pin1 (R) -> Teensy PD5  (XCK)
SN75176B:pin4 (D) -> not connected
SN75176B:pin3 (DE) -> L  
SN75176B:pin2 (NRE) -> L  

in this configuration i can measure fine clock coming from the EMAX (or EII: tried with this too, results were the same), and it can be seen arriving on the XCK.

as soon as i start EMXP and initiate transfer or receive, XCK will be pulled to ground! the oscilloscope shows almost no signal on the pin, which suggests that it went to output state.
 
What you think of this? I'd appreciate any suggestions.

Beyond this we wrote a single code that tests the Teensy's PD5 output by making it H, and it works.  

Then we wanted to check then if it could read its PD5 pin. We did a little program which reads PD5, and if it was high, it sets PD6 high, and it makes the orange LED lit up, as it wired there by default.  

For me it means that the PD5 on the Teensy works all right.

Btw Teensy++ will not work with the Teensy firmware (Windows will not detect the COM port, which proves this)

At this point we are completely clueless!!!! If there was anyone who could say anything about it, that would be none else, but you i guess.

Adam