C8051F310/1/2/3/4/5/6/7
28
Rev. 1.6
1.1.3. Additional Features
The C8051F31x SoC family includes several key enhancements to the CIP-51 core and peripherals to
improve performance and ease of use in end applications.
The extended interrupt handler provides 14 interrupt sources into the CIP-51 (as opposed to 7 for the stan-
dard 8051), allowing numerous analog and digital peripherals to interrupt the controller. An interrupt driven
system requires less intervention by the MCU, giving it more effective throughput. The extra interrupt
sources are very useful when building multi-tasking, real-time systems.
Eight reset sources are available: power-on reset circuitry (POR), an on-chip VDD monitor (forces reset
when power supply voltage drops below VRST as given in Table 9.1 on page 108), a Watchdog Timer, a
Missing Clock Detector, a voltage level detection from Comparator0, a forced software reset, an external
reset pin, and an errant Flash read/write protection circuit. Each reset source except for the POR, Reset
Input Pin, or Flash error may be disabled by the user in software. The WDT may be permanently enabled
in software after a power-on reset during MCU initialization.
The internal oscillator is factory calibrated to 24.5 MHz ±2%. An external oscillator drive circuit is also
included, allowing an external crystal, ceramic resonator, capacitor, RC, or CMOS clock source to generate
the system clock. If desired, the system clock source may be switched on-the-fly between the internal and
external oscillator circuits. An external oscillator can be extremely useful in low power applications, allow-
ing the MCU to run from a slow (power saving) external crystal source, while periodically switching to the
fast internal oscillator as needed.
Figure 1.10. On-Chip Clock and Reset
PCA
WDT
Missing
Clock
Detector
(one-
shot)
(Software Reset)
System Reset
Reset
Funnel
Px.x
Px.x
EN
SWRSF
Internal
Oscillator
System
Clock
CIP-51
Microcontroller
Core
Extended Interrupt
Handler
Clock Select
EN
XTAL1
XTAL2
External
Oscillator
Drive
Errant
FLASH
Operation
/RST
(wired-OR)
Power On
Reset
'0'
+
-
Comparator 0
C0RSEF
VDD
+
-
Supply
Monitor
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