Forum Discussion

Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
11 years ago

Bidirectional pin problem

Hi, I am using bidirectional SDIO pin for implementing an ADC SPI controller. As the ADC doesn't have separate SDO line, I Am left with no choice but to use the bidirectional pin. The ...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
11 years ago

Its because you've enabled the sdio from the testbench and inside the entity. So both are driving the bus at the same time. You need to ensure one side is always 'Z'.

Looking at the waveform, tri_en = '0', and bus_en = '1' (whcih sets tri_en internally to '0'), so the TB and the spi_interface are driving the same wire.