STR71x & STR73x I/O ports

AN2710

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STR71x & STR73x I/O ports

1.1

Functional description

Each of the general purpose I/O ports has three 16-bit Configuration registers (PC0, PC1,

PC2) and one 16-bit Data register (PD).

Subject to the specific hardware characteristics of each I/O port listed in the “Pin

description” table provided in the relevant STR7x datasheet, each port bit can be individually

configured as an input, output, alternate function, etc.

Each I/O port bit is freely programmable, however the I/O port registers have to be accessed

as 16-bit words. 32-bit or byte access is not allowed.

Figure 1 shows the basic structure of an I/O port bit.

Figure 1.

Basic structure of an I/O port bit

I/O pin

Analog input

Alternate function (OUT)

Alternate function (IN)

Push-pull

Tristate

Open drain

Weak push-p ull

TTL

CMOS

To on-chip peripheral

Read/Write

From on-chip peripheral

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