R8C28_08 Datasheet, PDF (167/473 Pages) Renesas Technology Corp – RENESAS 16-BIT SINGLE-CHIP MCU R8C FAMILY / R8C/2x SERIES

R8C/28 Group, R8C/29 Group
14. Timers
14.1.5 Pulse Period Measurement Mode
In pulse period measurement mode, the pulse period of an external signal input to the INT1/TRAIO pin is
measured (refer to Table 14.6 Specifications of Pulse Period Measurement Mode).
Figure 14.10 shows the TRAIOC Register in Pulse Period Measurement Mode and Figure 14.11 shows an
Operating Example of Pulse Period Measurement Mode.
Table 14.6 Specifications of Pulse Period Measurement Mode
Item
Specification
Count sources
f1, f2, f8, fOCO, fC32⁽²⁾
Count operations
• Decrement
• After the active edge of the measured pulse is input, the contents of the read-
out buffer are retained at the first underflow of timer RA prescaler. Then timer
RA reloads the contents in the reload register at the second underflow of
timer RA prescaler and continues counting.
Count start condition 1 (count start) is written to the TSTART bit in the TRACR register.
Count stop conditions
• 0 (count stop) is written to TSTART bit in the TRACR register.
• 1 (count forcibly stops) is written to the TSTOP bit in the TRACR register.
Interrupt request
generation timing
• When timer RA underflows or reloads [timer RA interrupt].
• Rising or falling of the TRAIO input (end of measurement period) [timer RA
interrupt]
INT1/TRAIO pin function Measured pulse input⁽¹⁾ (INT1 interrupt input)
TRAO pin function
Programmable I/O port
Read from timer
The count value can be read by reading registers TRA and TRAPRE.
Write to timer
• When registers TRAPRE and TRA are written while the count is stopped,
values are written to both the reload register and counter.
• When registers TRAPRE and TRA are written during the count, values are
written to the reload register and counter (refer to 14.1.1.1 Timer Write
Control during Count Operation).
Select functions
• Measurement period select
The TEDGSEL bit in the TRAIOC register selects the measurement period of
the input pulse.
• Measured pulse input pin select function
P1_7 or P1_5 is selected by the TIOSEL bit in the TRAIOC register.
• Digital filter function
Bits TIPF0 and TIPF1 in the TRAIOC register enable or disable the digital
filter and select the sampling frequency.
NOTES:
1. Input a pulse with a period longer than twice the timer RA prescaler period. Input a pulse with a
longer “H” and “L” width than the timer RA prescaler period. If a pulse with a shorter period is input to
the TRAIO pin, the input may be ignored.
2. For J, K version, fC32 cannot be selected.
Rev.2.10 Sep 26, 2008 Page 148 of 441
REJ09B0279-0210