How to switch JTAG-Pin3/ADBUS5 to input?

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How to switch JTAG-Pin3/ADBUS5 to input?

mjr

Hi,
does anyone know how that works?
>> get 3
DATA BITS: 11111100 01111111
READ PINVALS: fc7f
SETTING PINBYTES: fc7f
DIRECTION BITS: 00000000 00000000
READING PINS
DATA BITS: 11111100 01111111
READ PINMAP: fc7f
PIN 3 is High
while acbus1 (connected to nTRST pin of JTAG Header - input) goes to 0 adbus5 still stays high?

[deleted]

ADBUS5 (nTRST) should be high otherwise it will be resetting TAP controller.
Could you please let us know what are you trying to do?

mjr

thanks for your reply!
According to the FT_000109 document ADBUS5 can be used for input or output, I'd like to sense the input of 0V (which in my case would be the fault pin of another chip pulling down 3.3V to 0V).
However I should also be able to emulate that behaviour just by pulling ADBUS5 to ground, or am I wrong with that?
The voltage should go down to 0V and I should be able to read 0 from the ADBUS5 bit? As long as the direction bit is set to 0 for ADBUS5 the pin can be used as input?

mjr

I got it (partly).
The SN74LVC16T245 pulls the ADBUS5 pin high if I short the pin from the FTDI Chip the input is low and I can read the correct value, is there any way to disable this behaviour?
(I'm not using the JTAG functionality only the GPIO Pinout of the module).

[deleted]

IMHO You could disable buffer chip;
http://www.tiaowiki.com/w/TIAO_USB_Multi_Protocol_Adapter_User%27s_Manual#Buffer_Enable_Jumper
Please note that I'm not very experienced about the hardware modifications. If you are going to short pins, do it only at your own risk! But you better ask TIAO corp. via e-mail or ticket before shorting.

mjr

That jumper (and setting acbus3 high) doesn't seem to affect the adbus5 pin, it's still high...

[deleted]

I can recommend you to contact @Mike by Sending personal message to get his attention to this topic.