HD404629R Datasheet, PDF (38/157 Pages) Renesas Technology Corp – AS Microcomputer Incorporating a DTMF Generator Circuit

HD404629R Series
Subactive Mode: The OSC₁ and OSC₂ oscillator stops and the MCU operates with a clock generated by
the X1 and X2 oscillator. In this mode, functions except the A/D conversion operate. However, because
the operating clock is slow, the power dissipation becomes low, next to watch mode.
The CPU instruction execution speed can be selected as 244 µs or 122 µs by setting bit 2 (SSR2) of the
system clock select register (SSR: $029). Note that the SSR2 value must be changed in active mode. If the
value is changed in subactive mode, the MCU may malfunction.
When the STOP or SBY instruction is executed in subactive mode, the MCU enters either watch or active
mode, depending on the statuses of the low speed on flag (LSON: $020, bit 0) and the direct transfer on
flag (DTON: $020, bit 3).
Subactive mode is an optional function that the user must specify on the function option list.
Interrupt Frame: In watch and subactive modes, φ_CLK is applied to timer A and the INT₀Icircuit.
Prescaler W and timer A operate as the time-base and generate the timing clock for the interrupt frame.
Three interrupt frame lengths (T) can be selected by setting the miscellaneous register (MIS: $00C) (figure
18).
In watch and subactive modes, the timer-A/INT₀ interrupt is generated synchronously with the interrupt
frame. The interrupt request is generated synchronously with the interrupt strobe timing except during
transition to active mode. The falling edge of the INT₀ signal is input asynchronously with the interrupt
frame timing, but it is regarded as input synchronously with the second interrupt strobe clock after the
falling edge. An overflow and interrupt request in timer A is generated synchronously with the interrupt
strobe timing.
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