ST10F280_12 datasheet(113/239 Pages) STMICROELECTRONICS

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ST10F280

Parallel ports

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Figure 35.

Port 3 I/O and alternate functions

The port structure of the Port 3 pins depends on their alternate function (see Figure 36).

When the on-chip peripheral associated with a Port 3 pin is configured to use the alternate

input function, it reads the input latch, which represents the state of the pin, via the line

labeled “Alternate Data Input”. Port 3 pins with alternate input functions are:

T0IN, T2IN, T3IN, T4IN, T3EUD and CAPIN.

When the on-chip peripheral associated with a Port 3 pin is configured to use the alternate

output function, its “Alternate Data Output” line is ANDed with the port output latch line.

When using these alternate functions, the user must set the direction of the port line to

output (DP3.y=1) and must set the port output latch (P3.y=1). Otherwise the pin is in its

high-impedance state (when configured as input) or the pin is stuck at '0' (when the port

output latch is cleared).

When the alternate output functions are not used, the “Alternate Data Output” line is in its

inactive state, which is a high level ('1'). Port 3 pins with alternate output functions are:

T6OUT, T3OUT, TxD0 and CLKOUT.

When the on-chip peripheral associated with a Port 3 pin is configured to use both the

alternate input and output function, the descriptions above apply to the respective current

operating mode. The direction must be set accordingly. Port 3 pins with alternate

input/output functions are: MTSR, MRST, RxD0 and SCLK.

Note:

Enabling the CLKOUT function automatically enables the P3.15 output driver. Setting bit

DP3.15=’1’ is not required.

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