Port2 pins are also used to upload higher bytes of code to the internal program memory of the AT89S52 microcontroller and also used for verification of uploaded code. Some of these GPIO pins are used for in-circuit system programming interface and some are used as alternate functions for three 16-bit Timer/Counter pins. Like port 1, Port2 also has 8-bit dual-directional pins with internal pull-up resistors. Similar to port 0, Port1 also has 8-bit dual-directional pins with internal pull-up resistors. While using these pins for programming, we need to connect external pull-up resistors with these pins. Port0 pins are also used to upload lower bytes of code to the internal program memory of the AT89S52 microcontroller and also used for verification of uploaded code. But if they pulled high, they are used as digital output pins. If they are at a low state, they work as bidirectional high-impedance input pins. These general-purpose input/output pins can be configured for other operations as well when configured for that purpose using alternate functions of configuration registers. The pin configuration detail in tabular is mentioned below: Pin NumberĮxternal Access Enable/Flash Enable Supply pinĪll ports of AT89S52 are 8-bit which means each port has 8 multifunctional pins. But the pinout diagram is the same for all three packages. AT89S52 8-bit microcontroller is available in three packages.

Serial port programmer for at89s52