AN2710

STR71x & STR73x I/O ports

9/30

1.2.3

Input pull-up/pull-down configuration

When the I/O port is programmed as input pull-up/pull-down:

●

The output buffer is turned on in weak push-pull configuration and the firmware can

write the appropriate level into the output latch to activate the weak pull-up or pull-down

as required.

●

The data in the output latch drive the I/O pin (a logic zero activates a weak pull-down, a

logic one activates a weak pull-up).

●

A read access to the I/O Data register gets the input latch value.

Figure 3 shows the Input pull-up/pull-down configuration of the I/O port.

Figure 3.

Input pull-up/pull-down configuration

1.2.4

Output configuration

When the I/O port is programmed as output:

●

The output buffer is turned on in open drain or push-pull configuration

●

The data in the output latch drive the I/O pin

●

A read access to the I/O Data register gets the output latch value.

Figure 4 shows the output configuration of the I/O port bit.

I/O pin

Weak push-pull

Analog input

When AIEN = 1

PU

PD

Alternate function (IN)

Alternate function (OUT)

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