C8051F850-C-GM Datasheet, PDF (199/328 Pages) Silicon Laboratories – Low-Cost 8-bit MCU Family with up to 8 kB of Flash

21.2. Assigning Port I/O Pins to Analog and Digital Functions
Port I/O pins can be assigned to various analog, digital, and external interrupt functions. The port pins
assigned to analog functions should be configured for analog I/O, and port pins assigned to digital or
external interrupt functions should be configured for digital I/O.
21.2.1. Assigning Port I/O Pins to Analog Functions
Table 21.1 shows all available analog functions that require port I/O assignments. Table 21.1 shows the
potential mapping of port I/O to each analog function.
Table 21.1. Port I/O Assignment for Analog Functions
Analog Function
Potentially Assignable
Port Pins
SFR(s) used for
Assignment
ADC Input
Comparator0 Input
Comparator1 Input
Voltage Reference (VREF)
P0.0 - P1.7
P0.0 - P1.7
P0.0 - P1.7
P0.0
ADC0MX, PnSKIP,
PnMDIN
CPT0MX, PnSKIP,
PnMDIN
CPT1MX, PnSKIP,
PnMDIN
REF0CN, PnSKIP,
PnMDIN
Reference Ground (AGND)
P0.1
REF0CN, PnSKIP,
PnMDIN
21.2.2. 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. Table 21.2 shows all digital functions
available through the crossbar and the potential mapping of port I/O to each function.
Table 21.2. Port I/O Assignment for Digital Functions
Digital Function
Potentially Assignable Port Pins
UART0, SPI0, SMBus0, CP0, CP0A,
CP1, CP1A, SYSCLK, PCA0 (CEX0-
2 and ECI), T0, T1 or T2.
Any port pin available for assignment by the
crossbar. This includes P0.0 - P1.7 pins which
have their PnSKIP bit set to ‘0’.
Note: The crossbar will always assign UART0
pins to P0.4 and P0.5.
SFR(s) Used for
Assignment
XBR0, XBR1, XBR2
Any pin used for GPIO
P0.0 - P2.1
P0SKIP, P1SKIP,
P2SKIP
Rev. 1.0
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