EFM8UB2 Datasheet, PDF (5/50 Pages) Silicon Laboratories – The EFM8UB2 highlighted features are listed below

EFM8UB2 Data Sheet
System Overview
3.2 Power
All internal circuitry draws power from the VDD supply pin. External I/O pins are powered from the VIO supply voltage (or VDD on devi-
ces without a separate VIO connection), while most of the internal circuitry is supplied by an on-chip LDO regulator. Control over the
device power can be achieved by enabling/disabling individual peripherals as needed. Each analog peripheral can be disabled when
not in use and placed in low power mode. Digital peripherals, such as timers and serial buses, have their clocks gated off and draw little
power when they are not in use.
Table 3.1. Power Modes
Power Mode
Normal
Idle
Suspend
Shutdown
Details
Core and all peripherals clocked and fully operational
• Core halted
• All peripherals clocked and fully operational
• Code resumes execution on wake event
• Core and peripheral clocks halted
• Code resumes execution on wake event
• All internal power nets shut down
• 5V regulator remains active (if enabled)
• Pins retain state
• Exit on pin or power-on reset
Mode Entry
—
Set IDLE bit in PCON0
1. Switch SYSCLK to
HFOSC0
2. Set SUSPEND bit in
HFO0CN
1. Set STOPCF bit in
REG01CN
2. Set STOP bit in
PCON0
Wake-Up Sources
—
Any interrupt
USB0 Bus Activity
• RSTb pin reset
• Power-on reset
3.3 I/O
Digital and analog resources are externally available on the device’s multi-purpose I/O pins. Port pins P0.0-P3.7 can be defined as gen-
eral-purpose I/O (GPIO), assigned to one of the internal digital resources through the crossbar or dedicated channels, or assigned to an
analog function. Port pins P4.0-P4.7 can be used as GPIO. Additionally, the C2 Interface Data signal (C2D) is shared with P3.0 on
some packages.
• Up to 40 multi-functions I/O pins, supporting digital and analog functions.
• Flexible priority crossbar decoder for digital peripheral assignment.
• Two direct-pin interrupt sources with dedicated interrupt vectors (INT0 and INT1) available on P0 pins.
3.4 Clocking
The CPU core and peripheral subsystem may be clocked by both internal and external oscillator resources. By default, the system
clock comes up running from the 48 MHz oscillator divided by 4, then divided by 8 (1.5 MHz).
• Provides clock to core and peripherals.
• 48 MHz internal oscillator (HFOSC0), accurate to ±1.5% over supply and temperature corners: accurate to +/- 0.25% when using
USB clock recovery.
• 80 kHz low-frequency oscillator (LFOSC0).
• External RC, C, CMOS, and high-frequency crystal clock options (EXTCLK) for QFP48 packages.
• External CMOS clock option (EXTCLK) for QFP32 and QFN32 packages.
• Internal oscillator has clock divider with eight settings for flexible clock scaling: 1, 2, 4, or 8.
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