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Altera_Forum
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12 years ago

MAX 2 Shift Register delay problem

software : Quartus II Subscription Edition 9.1 sp2

use device : epm1270t144c5n (http://www.buyaltera.com/scripts/partsearch.dll?detail&name=544-1333-nd)

use kit : Developing board

pc os : Windows 7 32bit

I am developing 13ea SPI(Serial parallel interface) communication in the board.

In order to develope many spi module, I decided to use the CPLD.

First, It is implemented shift register Mega function in Quartus 2 to SPI TX, RX.

Physical layer is using optic fiber to rapidly communication.

In order to check communication status, TX ports(chip select, clock, data) is connected to RX ports.

I succeeded in the experiment 1:1 SPI communiation.

But this block is increased in number, the problem began to occur.

To implement 13 SPIs, it was copy/paste these blocks(SPI TX/RX modules), But shift register did not work well. 4 works fine so far. But, from 5 works(copy/paste) is not good. shift registers had a large delay acitvity. CPLD is less than 50% of the utilization.

1 Reply

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor

    It is likely the problem stems from the clock you have generated with and gates. Logic generated clocks can have high skew and be greatly affected by temperature.