C8051F321 Просмотр технического описания (PDF) - Unspecified

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C8051F321

Full Speed USB, 16k ISP FLASH MCU Family

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C8051F320/1

1.1.3. Additional Features

The C8051F320/1 SoC family includes several key enhancements to the CIP-51 core and peripherals to improve per-

formance and ease of use in end applications.

The extended interrupt handler provides 16 interrupt sources into the CIP-51 (as opposed to 7 for the standard 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 build-

ing multi-tasking, real-time systems.

Nine 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 10.1 on page 105), the USB controller (USB bus reset or a VBUS

transition), a Watchdog Timer, a Missing Clock Detector, a voltage level detection from Comparator0, a forced soft-

ware 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 12 MHz ±1.5%, and the internal oscillator period may be user pro-

grammed in ~0.25% increments. A clock recovery mechanism allows the internal oscillator to be used with the 4x

Clock Multiplier as the USB clock source in Full Speed mode; the internal oscillator can also be used as the USB

clock source in Low Speed mode. External oscillators may also be used with the 4x Clock Multiplier. 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. The system clock may be configured to use the internal oscillator, external

oscillator, or the Clock Multiplier output divided by 2. If desired, the system clock source may be switched on-the-fly

between oscillator sources. An external oscillator can be extremely useful in low power applications, allowing the

MCU to run from a slow (power saving) external clock source, while periodically switching to the internal oscillator

as needed.

Figure 1.4. On-Chip Clock and Reset

VDD

Px.x

Px.x

XTAL1

XTAL2

Internal

Oscillator

Clock

Multiplier

External

Oscillator

Drive

Supply

Monitor

+

-

Enable

Comparator 0

+

-

C0RSEF

Power On

Reset

'0'

Missing

Clock

Detector

(one-

shot)

EN

PCA

WDT

EN

Software Reset (SWRSF)

Errant

FLASH

Operation

(wired-OR)

Reset

Funnel

System

Clock

Clock Select

CIP-51

Microcontroller System Reset

Core

Extended Interrupt

Handler

USB

Controller

VBUS

Transition

/RST

Rev. 1.1

21

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