HD6473887 Datasheet, PDF (264/523 Pages) Renesas Technology Corp – Hitachi Single-Chip Microcomputer

9.7.3 Operation
1. 16-bit event counter operation
When bit CH2 is cleared to 0 in ECCSR, ECH and ECL operate as a 16-bit event counter. Figure
9-19 shows an example of the software processing when ECH and ECL are used as a 16-bit event
counter.
Start
Clear CH2 to 0
Clear CUEH, CUEL, CRCH, and CRCL to 0
Clear OVH and OVL to 0
Set CUEH, CUEL, CRCH, and CRCL to 1
End
Figure 9-19 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.
They can also be used as a 16-bit event counter by carrying out the software processing shown in
the example in figure 9-19. The operating clock source is asynchronous event input from the
AEVL pin. 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.
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