Lpc2000

You can write to IOPIN register, if you need ones and zeros appear at the 
same time. It works. Apearently just marked as RO in the UM. pin levels 
change accordingly as stated in the UM when you write to it.

Regards,

Kerem

----- Original Message ----- 
From: "Anton Erasmus" <antone@...>
To: <lpc2000@yahoogroups.com>
Sent: Thursday, January 06, 2005 10:23 PM
Subject: Re: [lpc2000] Writing to IOPIN on LPC21xx possible?


>
> On 4 Jan 2005 at 14:06, Aalt Lokhorst wrote:
>
>>
>> Hello All,
>>
>> In the Philips document 'UM_LPC21XX_LPC22XX_2.pdf' on page 137 I read:
>>
>>    Applications that require instanatneous appearance of zeros and
>>    ones on the respected parallel port can use direct access to port's
>>    corresponding GPIO Pin Value Register (IOPIN). Assuming that pins
>>    P0.8 to P0.15 are configured as output, write to IO0PIN:
>>
>>      IO0PIN = 0x0000 C700
>>
>>    will produce the same output as following sequence of writes:
>>
>>      IO0SET = 0x0000 C700
>>      IO0CLR = 0x0000 3800
>>
>>    Solution utilizing access to IO0SET and IO0CLR will take more steps
>>    compared to a single IO0PIN write access.
>>
>> The same document shows on page 135 that IO#PIN is a ReadOnly
>> register.
>>
>> Am I missing something, how can you write to a ReadOnly register?
>>
>
> Have you received any feedback on this from Philips ? I also notice that
> IOSET is defined as Read/Write. Why would one want to read the IOSET
> register. As far as I understand it, If one writes 1 to IOSET, then 1 to 
> IOCLR,
> the output pin would be 0, but the IOSET register will still indicate a 1, 
> hence
> making a read from this register meaningless.
>
> Regards
>   Anton Erasmus
>
>
>
> -- 
> A J Erasmus
>
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