C8051F340 Datasheet, PDF (253/282 Pages) List of Unclassifed Manufacturers – Full Speed USB Flash MCU Family

C8051F340/1/2/3/4/5/6/7
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. 0.5
253