C8051F335

The C8051F330/1/2/3/4/5 SoC family includes several key enhancements to the CIP-51 core and periph- erals 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 V_DD monitor (forces reset  when power supply voltage drops below V_RST  as given in Table 10.1 on page 104), a Watchdog Timer, a Missing Clock Detector, a voltage level detection from Comparator0, a forced software reset, an external reset pin, and an illegal Flash access 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 soft-ware after a power-on reset during MCU initialization.

The internal oscillator factory calibrated to 24.5 MHz ±2%. This internal oscillator period may be user pro-grammed in ~0.5% increments. An additional low-frequency oscillator is also available which facilitates low-power operation. An external oscillator drive circuit is 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 both internal and external oscillator circuits. An external oscil-lator can also be extremely useful in low power applications, allowing the MCU to run from a slow (power saving) source, while periodically switching to the fast (up to 25 MHz) internal oscillator as needed.