C8051F970-A-GM Datasheet, PDF (6/454 Pages) Silicon Laboratories – Low Power Capacitive Sensing MCU with up to 32 kB of Flash

C8051F97x
24.4.Special Function Registers for Selecting and Configuring the System Clock............ 247
24.5.Clock Selection Control Registers ............................................................................. 248
24.6.High Frequency Oscillator Registers ......................................................................... 251
24.7.External Oscillator Registers...................................................................................... 253
25. SmaRTClock (Real Time Clock, RTC0) ..........................................................................254
25.1.SmaRTClock Interface...............................................................................................255
25.1.1.Using RTC0ADR and RTC0DAT to Access SmaRTClock Internal Registers... 255
25.1.2.RTC0ADR Short Strobe Feature ....................................................................... 255
25.1.3.SmaRTClock Interface Autoread Feature ......................................................... 256
25.1.4.RTC0ADR Autoincrement Feature .................................................................... 256
25.2.SmaRTClock Clocking Sources.................................................................................257
25.2.1.Using the SmaRTClock Oscillator with a Crystal............................................... 257
25.2.2.Using the SmaRTClock Oscillator in Self-Oscillate Mode ................................. 258
25.2.3.Using the Low Frequency Oscillator (LFO) ....................................................... 258
25.2.4.Programmable Load Capacitance ..................................................................... 259
25.2.5.Automatic Gain Control (Crystal Mode Only) and SmaRTClock Bias Doubling 260
25.2.6.Missing SmaRTClock Detector..........................................................................262
25.2.7.SmaRTClock Oscillator Crystal Valid Detector.................................................. 262
25.3.SmaRTClock Timer and Alarm Function ...................................................................262
25.3.1.Setting and Reading the SmaRTClock Timer Value ......................................... 262
25.3.2.Setting a SmaRTClock Alarm............................................................................ 263
25.3.3.Software Considerations for Using the SmaRTClock Timer and Alarm ............ 264
25.4.RTC0 Control Registers............................................................................................. 265
26. Port I/O (Port 0, Port 1, Port 2, Port 3, Port 4, Port 5, Port 6, Crossbar, and Port Match)
278
26.1.General Port I/O Initialization ..................................................................................... 279
26.2.Assigning Port I/O Pins to Analog and Digital Functions ........................................... 280
26.2.1.Assigning Port I/O Pins to Analog Functions.....................................................280
26.2.2.Assigning Port I/O Pins to Digital Functions ...................................................... 281
26.2.3.Assigning Port I/O Pins to Fixed Digital Functions ............................................ 281
26.3.Priority Crossbar Decoder.......................................................................................... 282
26.4.Port I/O Modes of Operation ...................................................................................... 284
26.4.1.Configuring Port Pins For Analog Modes .......................................................... 284
26.4.2.Configuring Port Pins For Digital Modes ........................................................... 284
26.4.3.Port Drive Strength ............................................................................................ 284
26.5.Port Match.................................................................................................................. 285
26.6.Direct Read/Write Access to Port I/O Pins................................................................. 285
26.7.Port Configuration Registers...................................................................................... 286
26.8.Port I/O Control Registers.......................................................................................... 288
27. Reset Sources and Supply Monitor ............................................................................... 323
27.1.Power-On Reset ........................................................................................................ 324
27.2.Power-Fail Reset / Supply Monitor ............................................................................ 325
27.3.Enabling the VDD Monitor ......................................................................................... 326
27.4.External Reset ........................................................................................................... 326
27.5.Missing Clock Detector Reset.................................................................................... 326
27.6.PCA Watchdog Timer Reset...................................................................................... 326
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Rev 1.0