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Altera_Forum's avatar
Altera_Forum
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20 years ago

Problem with the IOWR and IORD

in an Ethernet program developed by IDE I do a test , writing: IOWR ( DM9000A_Base, 1, data); tmp=IORD ( DM9000A_Base ,1); Should not the tmp be the same with the data? the result is not ...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
20 years ago

It looks like you are trying to write to the DM900A ethernet chip status register, which is read-only (writing to it only clears status bits). A quick glance at the data sheet shows register 1 (the offset in your IOWR statement) is 00h at reset, so this is why you read 00h in the lower 8 bits. Upper bits are undefined if you are reading a byte.

Hope this helps.

Tim