ST10F271 datasheet(65/173 Pages) STMICROELECTRONICS

65 / 173 page

ST10F271

Parallel ports

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This is done by setting or clearing the direction control bit DPx.y of the pin before enabling

the alternate function.

There are port lines, however, where the direction of the port line is switched automatically.

For instance, in the multiplexed external bus modes of PORT0, the direction must be

switched several times for an instruction fetch in order to output the addresses and to input

the data.

Obviously, this cannot be done through instructions. In these cases, the direction of the port

line is switched automatically by hardware if the alternate function of such a pin is enabled.

To determine the appropriate level of the port output latches check how the alternate data

output is combined with the respective port latch output.

There is one basic structure for all port lines with only an alternate input function. Port lines

with only an alternate output function, however, have different structures due to the way the

direction of the pin is switched and depending on whether the pin is accessible by the user

software or not in the alternate function mode.

All port lines that are not used for these alternate functions may be used as general purpose

I/O lines.

ST10F271 数据表(PDF) 65 Page - STMicroelectronics