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Altera_Forum
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14 years ago

PIO Direction

hi all, I am using bidirectional pio for my design.Can some one tell me how to set the directions. I am using IOWR_ALTERA_AVALON_PIO_DIRECTION(PIO_DATA_BASE, 0); for using pio as output...
Altera_Forum's avatar
Altera_Forum
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14 years ago

Wrong!

You must write the same register but different bits

bit 0 = I/O nr. 1

bit 1 = I/O nr. 2

...

bit 7 = I/O nr. 8

For example:

IOWR_ALTERA_AVALON_PIO_DIRECTION(PIO_DATA_BASE, 0x43);

sets I/O 1,2 and 7 as outputs and all the others as inputs, since

0x43 is binary 01000011

The same applies for writing output values or reading inputs

In Qsys you have the option "Enable individual bit set/clear output register"; if you selected it, you can set/clear a single output through outset/outclear registers, otherwise you must write all of them jointly.

i.e. IOWR_ALTERA_AVALON_PIO_DATA(PIO_DATA_BASE, 0x42)

sets an high level on lines 2 and 7 (clearly they must have been previously set as outputs)

Reading is simpler: you call data = IORD_ALTERA_AVALON_PIO_DATA(PIO_DATA_BASE)

and simply test the required bits of data.