AM1808 I/O During Reset

Inderjit Bains

Other Parts Discussed in Thread: AM1808

The AM1808 datasheet has this statement as a footnote in many tables:

IPD = Internal Pulldown resistor; IPU = Internal Pullup resistor; CP[n] = configurable pull-up/pull-down (where n is the pin group) using
the PUPDENA and PUPDSEL registers in the System Module. The pull-up and pull-down control of these pins is not active until the
device is out of reset. During reset, all of the pins associated with these registers are weakly pulled down. If the application requires a
pull-up, an external pull-up can be used.

What is the value of the weak pull resistors down during reset?

over 12 years ago

0 BrandonAzbell over 12 years ago

TI__Guru 64490 points

The value of the internal pullup and pulldowns are specified as input current as indicated in Section 4.4 of the AM1808 datasheet.

0 Inderjit Bains over 12 years ago in reply to BrandonAzbell

Expert 2745 points

Just to be clear - there is no difference between the pulldown value during reset, and the pulldown value after reset has been deasserted (assuming the pin has a default pulldown).

0 Inderjit Bains over 12 years ago in reply to Inderjit Bains

Expert 2745 points

From the numbers, it would seem that an external pullup/pulldown resistor to oppose an internal pulldown/pullup resistor would need to be fairly low in value: around 1.1K for <10% or >90% VCC. If VCC is 3.3V, that would mean a supply current of +/- 3mA, which is fairly high.

Processors

Processors forum

AM1808 I/O During Reset