Recommended configuration sequence

AN2710

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4

Recommended configuration sequence

It appears that the safest sequence for writing the Port Configuration registers in most

situations is: PC2 - PC1 - PC0.

Exceptions to this would be in the following transitions:

1.

Input/Output to Output open drain

2.

Input/Output to Output push-pull

3.

Input/Output to Alternate Function open drain

4.

Input to Output open drain

5.

Input to Alternate Function open drain

In all of these cases the safest sequence for writing the PC registers is: PC0 - PC1 - PC2.

Note:

It is possible to have a level change on a pin during transition between open drain and push-

pull output modes. The resulting output level may be determined by the state of the GPIO

output, alternate function output and/or external pull-up/down (if any). The user needs to be

aware of the output state when changing the pin configuration.

4.1

From alternate push-pull

If the port is set to alternate push-pull, use the following sequences to change modes.

Table 4.

Alternate push-pull to analog input

PC2 - 0

1.

Input pull-up/pull-down.

PC1 - 0

Input

PC0 - 0

No change

Table 5.

Alternate push-pull to input

PC2 - 0

1.

Input pull-up/pull-down.

PC1 - 0

Input

PC0 - 1

No change

Table 6.

Alternate push-pull to Input pull-up/pull-down

PC2 - 0

1.

Input pull-up/pull-down.

PC1 - 1

No change

PC0 - 1

No change

Table 7.

Alternate push-pull to output open drain

PC2 - 1

No change

PC1 - 0

Output push-pull

PC0 - 0

Output open drain