HD6433937 Datasheet, PDF (119/521 Pages) Hitachi Semiconductor – Hardware Manual

5.3.5 Notes on External Input Signal Changes before/after Standby Mode
1. When external input signal changes before/after standby mode or watch mode
When an external input signal such as IRQ or WKP is input, both the high- and low-level
widths of the signal must be at least two cycles of system clock ø or subclock ø (referred to
SUB
together in this section as the internal clock). As the internal clock stops in standby mode and
watch mode, the width of external input signals requires careful attention when a transition is
made via these operating modes.
2. When external input signals cannot be captured because internal clock stops
The case of falling edge capture is illustrated in figure 5-3
As shown in the case marked "Capture not possible," when an external input signal falls
immediately after a transition to active (high-speed or medium-speed) mode or subactive
mode, after oscillation is started by an interrupt via a different signal, the external input signal
cannot be captured if the high-level width at that point is less than 2 t_cyc or 2 t_subcyc.
3. Recommended timing of external input signals
To ensure dependable capture of an external input signal, high- and low-level signal widths of
at least 2 t_cyc or 2 t_subcyc are necessary before a transition is made to standby mode or watch
mode, as shown in "Capture possible: case 1."
External input signal capture is also possible with the timing shown in "Capture possible: case
2" and "Capture possible: case 3," in which a 2 t_cyc or 2 t_subcyc level width is secured.
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