HD6473847RHV Datasheet, PDF (278/546 Pages) Renesas Technology Corp – Renesas 8-Bit Single-Chip Microcomputer H8 Family / H8/300L Super Low Power Series

Section 9 Timers
Start
Clear CH2 to 0
Set ACKL1, ACKL0, ALEGS1, and ALEGS0
Clear CUEH, CUEL, CRCH, and CRCL to 0
Clear OVH and OVL to 0
Set CUEH, CUEL, CRCH, and CRCL to 1
End
Figure 9.8 Example of Software Processing when Using ECH and ECL as
16-Bit Event Counter
As CH2 is cleared to 0 by a reset, ECH and ECL operate as a 16-bit event counter after a reset,
and as ACKL1 and ACKL0 are cleared to B′00, the operating clock is asynchronous event input
from the AEVL pin (using falling edge sensing).
When the next clock is input after the count value reaches H'FF in both ECH and ECL, ECH and
ECL overflow from H'FFFF to H'0000, the OVH flag is set to 1 in ECCSR, the ECH and ECL
count values each return to H'00, and counting up is restarted. When overflow occurs, the IRREC
bit is set to 1 in IRR2. If the IENEC bit in IENR2 is 1 at this time, an interrupt request is sent to
the CPU.
8-Bit Counter Operation: When bit CH2 is set to 1 in ECCSR, ECH and ECL operate as
independent 8-bit event counters.
φ/2, φ/4, φ/8, or AEVH pin input can be selected as the input clock source for ECH by means of
bits ACKH1 and ACKH0 in ECCR, and φ/2, φ/4, φ/8, or AEVL pin input can be selected as the
input clock source for ECL by means of bits ACKL1 and ACKL0 in ECCR.
Input sensing is selected with bits AHEGS1 and AHEGS0 when AEVH pin input is selected, and
with bits ALEGS1 and ALEGS0 when AEVL pin input is selected.
The input clock is enabled only when IRQAEC is high or IECPWM is high. When IRQAEC is
low or IECPWM is low, the input clock is not input to the counter, which therefore does not
operate. Figure 9.9 shows an example of the software processing when ECH and ECL are used as
8-bit event counters.
Rev. 7.00 Mar. 08, 2010 Page 246 of 510
REJ09B0024-0700