16-Bit Timer Capture; Operation - Panasonic F77G User Manual

Chapter 7 16-bit Timer
7-9

16-bit Timer Capture

7-9-1

Operation

The value of a binary counter is stored to register at the timing of the external interrupt input signal, or the
timing of writing operation with an arbitrary value to the capture register.
Capture Operation with External Interrupt Signal as a Trigger (Timer 7)
Capture trigger of input capture function is generated at the external interrupt signal that passed through
the external interrupt interface block. The capture trigger is selected by the timer 7 mode register 2
(TM7MD2) and the external interrupt control register (IRQ0ICR, IRQ1ICR, IRQ2ICR, IRQ3ICR).
Here are the capture trigger to be selected and the interrupt flag setup.
Capture trigger source
IRQ0 falling edge
IRQ0 rising edge
IRQ0 both edge
IRQ1 falling edge
IRQ1 rising edge
IRQ1 both edge
IRQ2 falling edge
IRQ2 rising edge
IRQ2 both edge(*)
IRQ3 falling edge
IRQ3 rising edge
IRQ3 both edge(*)
The external interrupt 2 (IRQ2) and the external interrupt 3 (IRQ3) has the function of both
edges interrupt. But, that function cannot be used when the input capture should be gener-
ated at both edges. [table 7-9-1(*)]
When capture trigger is activated at both edges of an external interrupt, the high precision pulse width
measurement that measures the width of "H" period and "L" period of input signal constantly, is possible
VII - 34
16-bit Timer Capture
Table 7-9-1
Timer 7 m ode register 2
T7ICT1-0 T7ICEDG
00(IRQ0) 1
00(IRQ0) 1
00(IRQ0) 0
01(IRQ1) 1
01(IRQ1) 1
01(IRQ1) 0
10(IRQ2) 1
10(IRQ2) 1
10(IRQ2) 0
11(IRQ3) 1
11(IRQ3) 1
11(IRQ3) 0
Capture Trigger
External interrupt n
Both edges interrupt
control register
control register (EDGDT)
(IRQnICR)
REDGn (bp5) EDGSEL3
0 -
1 -
0 -
1 -
0 -
1 -
0 -
1 -
0 -
1 -
0 -
1 -
0 0
1 0
0 0
1 0
Interrupt starting edge of
external interrupt n
EDGSEL2
- IRQ0 falling edge
- IRQ0 rising edge
- IRQ0 falling edge
- IRQ0 rising edge
- IRQ1 falling edge
- IRQ1 rising edge
- IRQ1 falling edge
- IRQ1 rising edge
0 IRQ2 falling edge
0 IRQ2 rising edge
0 IRQ2 falling edge
0 IRQ2 rising edge
- IRQ3 falling edge
- IRQ3 rising edge
- IRQ3 falling edge
- IRQ3 rising edge