Lpc2000

Other  optin is to have a variable always set according to the setting of the port every time.
for example you want to set  value 0x3045 to port 1 you can sya 

temp1 = 0x3045;
IO1PIN = temp1;

next time you want to change port 1  all you do is take existing value not by reading port but from temp1 varaible 

so you canm say :
temp1 &= 0xfffffff0 ; for last eight bit
temp1 |= 0x04;
IO1PIN = temp1;

keep in mind you have to keep track of IO1PIN by updating temp1 every time you change IO1PIN. This is an old technique used in firmware for microcontroller for which it is not possible to know the status of the output port.

kb shah
  ----- Original Message ----- 
  From: Aalt Lokhorst 
  To: lpc2000@yahoogroups.com 
  Sent: Tuesday, April 19, 2005 4:38 AM
  Subject: Re: [lpc2000] Re: Writing 8 bits on the IO port


  Hello Kimi and Rob,

  Rob his solution reads the current port status. In most situations this 
  is no problem. But it is a read/modify write situation and I don't know 
  if you always want that. You can also use something like this (not 
  tested but I think it is clear what I mean):

     IO0SET = ( Data<<14) & 0x3FC0;
     IO0CLR = (~Data<<14) & 0x3FC0;

  It changes the data bus in two steps so there will be intermediate 
  values on the bus. This is not a problem if you use separate control 
  lines to control when the data is valid. Don't forget to set the 
  direction of the pins according to the read or write situation and avoid 
  collisions as a result of two devices driving the bus at the same time.

  Best regards,

  -- 
  ==============================
  Aalt Lokhorst
  Schut Geometrische Meettechniek bv
  Duinkerkenstraat 21
  9723 BN Groningen
  P.O. Box 5225
  9700 GE Groningen
  The Netherlands
  Tel: +31-50-5877877
  Fax: +31-50-5877899
  E-mail: Lokhorst@...
  ==============================

  dibosco wrote:
  > 
  > I've done an almost identical thing and just got my char value to
  > write, chifted into its correct position in a temporary value in a
  > long. Then read what's currently on the output port into another
  > temporary long, ANDed out the relevant eight bits, then ORed into this
  > the new bits which are in the correct positiion in the temporary long.
  > This value is then written to the output port.
  > 
  > Not sure that reads very well. Some code:
  > 
  > // put char to write in temp and shift it to correct position
  > Temp1 = NewVal << 14;
  > // Get current output value of PORT0
  > Temp2 = IO0PIN;
  > // AND out P0.14-21
  > Temp2 &= ~0x3FC000;
  > //OR in what you *do* want to write.
  > Temp2 |= Temp1;
  > // Then write to the port
  > IO0PIN = Temp1;
  > 
  > Check the syntax of that last line's right!
  > 
  > And you've written the value to the port. :-)
  > 
  > Cheers,
  > 
  > Rob
  > 
  > --- In lpc2000@yahoogroups.com, "acetoel" <acetoel@y...> wrote:
  >  >
  >  > Hello,
  >  >
  >  > I making a little protocol to interfase between a LPC2106 and an Atmel
  >  > 8bits MCU. My idea is to use an 8bit data bus (P0.14 to P0.21) for
  >  > sending and receiving bytes, and then a few control lines (Busy/Ready,
  >  > Clock, Enable, Command/Data).
  >  > How can I write a byte variable (char) to that 8bit port? and how can
  >  > I read that data port, and save it on a variable? being P0.14 is the
  >  > Least Significative bit.
  >  >
  >  > Thanks
  >  > Kimi
  > 
  > 
  > 
  > 
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