1.9. Port Input/Output
C8051F52x/F52xA/F53x/F53xA devices include up to 16 I/O pins. Port pins are organized as two byte-
wide ports. The port pins behave like typical 8051 ports with a few enhancements. Each port pin can be
configured as a digital or analog I/O pin. Pins selected as digital I/O can be configured for push-pull or
open-drain operation. The “weak pullups” that are fixed on typical 8051 devices may be globally disabled
to save power.
The Digital Crossbar allows mapping of internal digital system resources to port I/O pins. On-chip
counter/timers, serial buses, hardware interrupts, and other digital signals can be configured to appear on
the port pins using the Crossbar control registers. This allows the user to select the exact mix of general-
purpose port I/O, digital, and analog resources needed for the application.
*Available in 'F53x/'F53xA
Figure 1.9. Port I/O Functional Block Diagram
24 Rev. 1.4