S3F84B8_UM_REV 1.00 9 I/O PORTS9-19 I/O PORTS9.1 OVERVIEW OF I/O PORTSThe S3F84B8 microcontroller has three bit-programmable I/O ports (P0, P1, and P2) and 17 I/O pins. Each portcan be easily configured to meet the application design requirements. The CPU accesses ports by directly writingor reading the port registers. No special I/O instructions are required.Table 9-1 provides a general overview of the S3F84B8 I/O port functions.Table 9-1 S3F84B8 Port Configuration OverviewPort Configuration Options0 I/O port with bit-programmable pins. Configurable to input or push-pull output mode. Pull-upresistors can be assigned by the software. Pins can also be assigned individually as alternativefunction pins.1 I/O port with bit-programmable pins. Configurable to input or push-pull output mode. Pull-upresistors can be assigned by the software. Pins can also be assigned individually as alternativefunction pins.2 I/O port with bit-programmable pins. Configurable to input mode or push-pull output mode. Pins canalso be assigned individually as alternative function pins.For better Electrical Fast transients Test (EFT) performance, when P10, P11, P12, P24, and P25 (with alternativefunction as comparator input) are configured as input pins, it is recommended to add 102pF capacitor externally.9.1.1 PORT DATA REGISTERSTable 9-2 provides an overview of the register locations of all three S3F84B8 I/O port data registers. Dataregisters for ports 0, 1, and 2 have the general format, as shown in Figure 9-1.Table 9-2 Port Data Register SummaryRegister Name Mnemonic Decimal Hex Location R/WPort 0 data register P0 224 E0H Set1, Bank0 R/WPort 1 data register P1 225 E1H Set1, Bank0 R/WPort 2 data register P2 226 E2H Set1, Bank0 R/W
