C8051F336/7/8/9
20.2.2. Assigning Port I/O Pins to Digital Functions
Any Port pins not assigned to analog functions may be assigned to digital functions or used as GPIO. Most
digital functions rely on the Crossbar for pin assignment; however, some digital functions bypass the
Crossbar in a manner similar to the analog functions listed above. Port pins used by these digital
functions and any Port pins selected for use as GPIO should have their corresponding bit in
PnSKIP set to ‘1’. Table 20.2 shows all available digital functions and the potential mapping of Port I/O to
each digital function.
Table 20.2. Port I/O Assignment for Digital Functions
Digital Function
Potentially Assignable Port Pins
SFR(s) used for
Assignment
UART0, SPI0, SMBus, CP0, Any Port pin available for assignment by the
CP0A, SYSCLK, PCA0 Crossbar. This includes P0.0 - P2.3 pins which
(CEX0-2 and ECI), T0 or T1. have their PnSKIP bit set to ‘0’.
Note: The Crossbar will always assign UART0
pins to P0.4 and P0.5.
XBR0, XBR1
Any pin used for GPIO
P0.0 - P2.4
P0SKIP, P1SKIP,
P2SKIP
20.2.3. Assigning Port I/O Pins to External Digital Event Capture Functions
External digital event capture functions can be used to trigger an interrupt or wake the device from a low
power mode when a transition occurs on a digital I/O pin. The digital event capture functions do not require
dedicated pins and will function on both GPIO pins (PnSKIP = ’1’) and pins in use by the Crossbar
(PnSKIP = ‘0’). External digital event capture functions cannot be used on pins configured for analog I/O.
Table 20.3 shows all available external digital event capture functions.
Table 20.3. Port I/O Assignment for External Digital Event Capture Functions
Digital Function
Potentially Assignable Port Pins
SFR(s) used for
Assignment
External Interrupt 0
External Interrupt 1
Port Match
P0.0 - P0.7
P0.0 - P0.7
P0.0 - P1.7
IT01CF
IT01CF
P0MASK, P0MAT
P1MASK, P1MAT
130
Rev. 0.2
SILICON [ SILICON ]
