C8051F54X_14 Datasheet, PDF (152/275 Pages) Silicon Laboratories – Mixed Signal ISP Flash MCU Family

C8051F54x
Port
P0
P1
P2
P3
Special
Function
Signals
P2.2-P2.7, P3.0 only available on
the 32-pin packages
PIN I/O 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
0
UART_TX
UART_RX
SCK
MISO
MOSI
NSS
SDA
*NSS Is only pinned out in 4-wire SPI Mode
SCL
CP0
CP0A
CP1
CP1A
SYSCLK
CEX0
CEX1
CEX2
CEX3
CEX4
CEX5
ECI
T0
T1
LIN_TX
LIN_RX
011001000000000000000000
0
P0SKIP[0:7]
P1SKIP[0:7]
P2SKIP[0:7]
P3SKIP[0]
Figure 18.4. Crossbar Priority Decoder in Example Configuration
18.4. Port I/O Initialization
Port I/O initialization consists of the following steps:
1. Select the input mode (analog or digital) for all Port pins, using the Port Input Mode register (PnMDIN).
2. Select the output mode (open-drain or push-pull) for all Port pins, using the Port Output Mode register
(PnMDOUT).
3. Select any pins to be skipped by the I/O Crossbar using the Port Skip registers (PnSKIP).
4. Assign Port pins to desired peripherals.
5. Enable the Crossbar (XBARE = 1).
All Port pins must be configured as either analog or digital inputs. Any pins to be used as Comparator or
ADC inputs should be configured as an analog inputs. When a pin is configured as an analog input, its
weak pullup, digital driver, and digital receiver are disabled. This process saves power and reduces noise
on the analog input. Pins configured as digital inputs may still be used by analog peripherals; however this
practice is not recommended.
Additionally, all analog input pins should be configured to be skipped by the Crossbar (accomplished by
setting the associated bits in PnSKIP). Port input mode is set in the PnMDIN register, where a 1 indicates a
digital input, and a 0 indicates an analog input. All pins default to digital inputs on reset. See SFR Definition
18.13 for the PnMDIN register details.
152
Rev. 1.1