>From the description, they would appear to be writeable addresses that would 
>allow you alter select outputs without knowing the current state of the 
>output.  So writing an 0x0080 to 0688 would clear bit 7 to 0 and leave the 
>others in their current state.  Writing 0x0808 to 068c would set bits 11 and 3 
>to 1 without changing any other.  That's how I read it based on what you just 
>posted, so YMMV.

-Jed

On Jan 10, 2013, at 8:03 PM, Matt Dainty <[email protected]> wrote:

> I've been writing a driver for the GPIO as implemented by the FPGA on
> the net6501 and I was wondering if someone (Soren?) could clarify the
> purpose of some of the I/O ports.
> 
>> From the archive, I have the following information regarding the GPIO:
> 
>> I/O Port 0680  bit 15..0  gpio input
>>         0684  bit 15..0  gpio output
>>         0688  bit 15..0  gpio reset bit when '1'
>>         068C  bit 15..0  gpio set bit when '1'
>>         0690  bit 15..0  gpio dir '0'=input, '1'=output
> 
> The first, second and fifth I/O ports seem fairly obvious; read state
> from the first, write state to the second in the case of output pins
> and change the direction with the fifth but I can't work out what the
> third and fourth I/O ports are used for, they always seem to read as 0.
> 
> Could someone explain how they're supposed to be used?
> 
> Matt
> -- 
> "Never rub another man's rhubarb."
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