HD4048412FS datasheet(37/127 Pages) RENESAS

37 / 127 page

HD404849 Series

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).

Interrupt Frame: In watch and subactive modes,

CLK is applied to timer A and theINT0 circuit. 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, a timer-A/

INT

0 interrupt is generated synchronously with the interrupt

frame. An interrupt request is generated synchronously with an interrupt strobe except during transition to

active mode. The falling edge of the

INT

0 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.

Direct Transition from Subactive Mode to Active Mode: Available by controlling the direct transfer on

flag (DTON: $020, bit 3) and the low speed on flag (LSON: $020, bit 0). The procedures are described

below:

• Set LSON to 0 and DTON to 1 in subactive mode.

• Execute the STOP or SBY instruction.

• The MCU automatically enters active mode from subactive mode after waiting for the MCU internal

processing time and oscillation stabilization time (figure 19).

Notes: 1. The DTON flag ($020, bit 3) can be set only in subactive mode. It is always reset in active

mode.

2. The transition time (T

D) from subactive mode to active mode:

RC < TD < T + tRC

Subactive mode

Interrupt strobe

Direct transfer

completion timing

MCU internal

processing period

Oscillation

stabilization

time

Active mode

STOP/SBY instruction execution

(Set LSON = 0, DTON = 1)

Interrupt frame length

Oscillation stabilization period

Figure 19 Direct Transition Timing

HD4048412FS Datasheet(PDF) 37 Page - Renesas Technology Corp

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