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Timer 0 and 1/or ack

 
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jacqueskleynhans



Joined: 10 Apr 2008
Posts: 109
Location: Cape Town, South Africa

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Timer 0 and 1/or ack
PostPosted: Sun Oct 24, 2010 7:01 am     Reply with quote
Hi Guys, I need to run the following code 8mil times.

Code:

output_low(read_clk);
output_high(read_clk);
data = PORTD;
printf("%u \n\r", data);


This is to read data back from a 8MB sram memory connected to a fpga with buffered image data to a pc through putty or something similar. Data will be available on the rising edge of the read clk.

Do I use a timer or generate a ack from the fpga when the 8mil mark is reached. Also is the little snippet implementable ? Or is there a better way of doing this ?

Thx in advance
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SherpaDoug



Joined: 07 Sep 2003
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PostPosted: Sun Oct 24, 2010 11:31 am     Reply with quote
I guess I don't understand the question. What is wrong with counting to 8M times through the loop? A simple int32 will do the job.
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jacqueskleynhans



Joined: 10 Apr 2008
Posts: 109
Location: Cape Town, South Africa

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PostPosted: Sun Oct 24, 2010 12:07 pm     Reply with quote
the problem is not the int32 but the time it will take to make a signal high then low read a byte from portd then transmit it to the computer, then increment the counter.
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PCM programmer



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PostPosted: Sun Oct 24, 2010 12:13 pm     Reply with quote
You didn't give your PIC. But consider using a PIC such as the 18F4550
that has a Streaming Parallel Port.
http://www.ccsinfo.com/forum/viewtopic.php?t=34952

Read the section in the 18F4550 data sheet on it.
SherpaDoug



Joined: 07 Sep 2003
Posts: 1640
Location: Cape Cod Mass USA

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PostPosted: Sun Oct 24, 2010 2:58 pm     Reply with quote
In the code you show, by far the longest part will be the printf(). If your data is 1 byte, the \n\r will add two more bytes, tripling the time it takes to send the data. Even at the highest baud rates this will be the bottleneck.
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