how to communicate with a new external peripheral

Altera_Forum · ‎11-24-2005

sorry, my english is poor.

i want to connect with Nios II system(SOPC Builder) and an altsynram(User Logic)

now, i want to write a data (16 signed bits) to altsynram(data bits=16, addr bits=8)

but the altsynram's CLK is connect to external oscillator (12.288MHz), i can't write data to altsynram properly.(my Nios II system's CLK is 50MHz) Orz

example:

IOWR(RAM_BASE, 0x00, 0x1234);

IOWR(RAM_BASE, 0x01, 0x5678);

x=IORD(RAM_BASE, 0x00);

y=IORD(RAM_BASE, 0x01);

correct answer should be x=0x1234, y=0x5678, but sometimes x=0x0000, y=0x5678 or x=0x1234, y=0x1234 or etc.

my Nios II system and external oscillator are asynchronous, how to improve it??

thx <(_ _)>

Altera_Forum · ‎11-25-2005

Hi kewang,

Your avalon interface must meet the timing requirements of your altsyncram. There

are many ways to do this ... and the appropriate solution will depend on your

particular requirements. The easiest is to add some glue logic that takes advantage

of the avalon waitrequest signal -- to make sure the avalon side meets the minimum

setup and hold times for your ram.

See http://www.altera.com/literature/manual/mnl_avalon_spec.pdf (http://www.altera.com/literature/manual/mnl_avalon_spec.pdf)

Regards,

--Scott