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I/O Analog Multiplexer in EnCoReV | Cypress Semiconductor

I/O Analog Multiplexer in EnCoReV

Summary: 1 Reply, Latest post by PRJI on 24 Aug 2012 09:50 AM PDT
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kollesok's picture
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According to the Technical Reference Manual, CY7C64xx EnCoReV devices have a device-wide  Analog I/O Multiplexer bus. Is it possible to use this bus to remap GPIO pins? For example, I would like to remap P1_6 (TIMEROUT) to P1_7 to simplify my PCB design. I have tried to do this on the development board and have noticed an interesting behavior for the following design:

P1_6 is configured to output 32kHz signal from Timer (drive mode 'Strong', VDD = 5V),  connected to the I/O Mux. bus

P1_7: drive mode: High-Z input, connected to the I/O Mux bus

The signal on P1_6 is output as expected, on P1_7 I can see with oscilloscope the same signal but with amplitude of 3V.

When I increase the frequency of the signal, the amplitude drops down to 2V.

It seems I am using the hardware improperly, the Reference Manual is not helpful at all, there is a mysterious phrase: 'You are able to connect any number of pins simultaneously, and dedicated support circuitry allows selected pins to be alternately charged high or connected to the bus '. So there is some analog circuitry that distorts my signal. Can please anyone clarify what is really going on on this I/O Multiplexer bus? 

Thank you.

prji's picture
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