C8051F709-GQR Silicon Labs, C8051F709-GQR Datasheet - Page 280

• Manufacturer Part Number: C8051F709-GQR
• Description: 8-bit Microcontrollers - MCU 8kB 32B EEPROM Cap Sense
• Manufacturer: Silicon Labs

Specifications of C8051F709-GQR

• Rohs: yes
• Core: 8051
• Processor Series: C8051
• Data Bus Width: 8 bit

C8051F70x/71x
33.3.3. Comparator 0 Capture Mode
The capture mode in Timer 3 allows Comparator 0 rising edges to be captured with the timer clocking from
the system clock or the system clock divided by 12. Timer 3 capture mode is enabled by setting TF3CEN
to 1 and T3SPLIT to 0.
When capture mode is enabled, a capture event will be generated on every Comparator 0 rising edge.
When the capture event occurs, the contents of Timer 3 (TMR3H:TMR3L) are loaded into the Timer 3
reload registers (TMR3RLH:TMR3RLL) and the TF3H flag is set (triggering an interrupt if Timer 3 inter-
rupts are enabled). By recording the difference between two successive timer capture values, the
Comparator 0 period can be determined with respect to the Timer 3 clock. The Timer 3 clock should be
much faster than the capture clock to achieve an accurate reading.
This mode allows software to determine the time between consecutive Comparator 0 rising edges, which
can be used for detecting changes in the capacitance of a capacitive switch, or measuring the frequency of
a low-level analog signal.
280
External Clock / 8
Comparator 0
SYSCLK / 12
SYSCLK
Output
T3XCLK
0
1
Figure 33.9. Timer 3 Capture Mode Block Diagram
T
M
H
3
M
T
3
L
0
1
CKCON
M
H
T
2
T
M
2
L
M
T
1
TF3CEN
M
T
0
S
C
A
1
TR3
S
C
A
0
Capture
Rev. 1.0
TCLK
TMR3RLL TMR3RLH
TMR3L
TMR3H
TF3CEN
T3SPLIT
TF3LEN
T3XCLK
TF3H
TF3L
TR3
Interrupt