Asynchronous Event Counter Operation Modes; Application Notes - Renesas H8 Series Hardware Manual

8-bit single-chip microcomputer

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Section 9 Timers

Asynchronous Event Counter Operation Modes

Asynchronous event counter operation modes are shown in table 9.21.

Table 9.21 Asynchronous Event Counter Operation Modes

Reset Active

Functions Functions Retained *

Functions Functions Retained *

Functions Functions Retained *

Functions Functions Functions *

Functions Functions Functions *

Functions Functions Retained *

Functions Functions Retained

Notes: 1. When an asynchronous external event is input, the counter increments but the counter

overflow H/L flags are not affected.

2. Operates when asynchronous external events are selected; halted and retained

3. Clock control by IRQAEC operates, but interrupts do not.

4. As the clock is stopped in module standby mode, IRQAEC has no effect.

1. When reading the values in ECH and ECL, the correct value will not be returned if the event

counter increments during the read operation. Therefore, if the counter is being used in the 8-

bit mode, clear bits CUEH and CUEL in ECCSR to 0 before reading ECH or ECL. If the

counter is being used in the 16-bit mode, clear CUEL only to 0 before reading ECH or ECL.

2. Use a clock with a frequency of up to 16 MHz for input to the AEVH and AEVL pins, and

ensure that the high and low widths of the clock are at least half the OSC clock cycle duration.

The duty cycle is immaterial.

Rev. 7.00 Mar 10, 2005 page 328 of 652

REJ09B0042-0700