C8051F342 View Datasheet(PDF) - Silicon Laboratories

Part Name

Description

Manufacturer

C8051F342

Full Speed USB Flash MCU Family

Silicon Laboratories 

C8051F340/1/2/3/4/5/6/7/8/9/A/B/C/D

21.2.3. Timer 2 Capture Modes: USB Start-of-Frame or LFO Falling Edge

When T2CE = ‘1’, Timer 2 will operate in one of two special capture modes. The capture event can be

selected between a USB Start-of-Frame (SOF) capture, and a Low-Frequency Oscillator (LFO) Falling

Edge capture, using the T2CSS bit. The USB SOF capture mode can be used to calibrate the system clock

or external oscillator against the known USB host SOF clock. The LFO falling-edge capture mode can be

used to calibrate the internal Low-Frequency Oscillator against the internal High-Frequency Oscillator or

an external clock source. When T2SPLIT = ‘0’, Timer 2 counts up and overflows from 0xFFFF to 0x0000.

Each time a capture event is received, the contents of the Timer 2 registers (TMR2H:TMR2L) are latched

into the Timer 2 Reload registers (TMR2RLH:TMR2RLL). A Timer 2 interrupt is generated if enabled.

TMR2CN

TTTTTTTT

FFF 2 2R2 2

2 2 2CS2CX

HL LEP SC

E L SL

NI K

T

CKCON

T T T T T T SS

3 3 2 2 1 0CC

MMMMMMA A

HLHL 10

SYSCLK / 12

0

External Clock / 8

1

SYSCLK

0

TR2

1

TL2

Overflow

To SMBus

TCLK TMR2L TMR2H

USB Start-of-Frame (SOF)

Low-Frequency Oscillator

Falling Edge

0

Capture TMR2RLL TMR2RLH

1

T2CSS

Enable

Interrupt

Figure 21.6. Timer 2 Capture Mode (T2SPLIT = ‘0’)

To ADC,

SMBus

Rev. 1.3

245

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