TMP86CS49UG datasheet(34/252 Pages) TOSHIBA

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Page 20

2. Operational Description

2.2 System Clock Controller

TMP86CS49UG

STOP mode is released by the following sequence.

1. In the dual-clock mode, when returning to NORMAL2, both the high-frequency and low-

frequency clock oscillators are turned on; when returning to SLOW1 mode, only the low-

frequency clock oscillator is turned on. In the single-clock mode, only the high-frequency

clock oscillator is turned on.

2. A warm-up period is inserted to allow oscillation time to stabilize. During warm up, all

internal operations remain halted. Four different warm-up times can be selected with the

SYSCR1<WUT> in accordance with the resonator characteristics.

3. When the warm-up time has elapsed, normal operation resumes with the instruction follow-

ing the STOP mode start instruction.

Note 1: When the STOP mode is released, the start is made after the prescaler and the divider of the

timing generator are cleared to "0".

Note 2: STOP mode can also be released by inputting low level on the RESET pin, which immediately

performs the normal reset operation.

Note 3: When STOP mode is released with a low hold voltage, the following cautions must be observed.

The power supply voltage must be at the operating voltage level before releasing STOP mode.

The RESET pin input must also be “H” level, rising together with the power supply voltage. In this

case, if an external time constant circuit has been connected, the RESET pin input voltage will

increase at a slower pace than the power supply voltage. At this time, there is a danger that a

reset may occur if input voltage level of the RESET pin drops below the non-inverting high-level

input voltage (Hysteresis input).

Note 1: The warm-up time is obtained by dividing the basic clock by the divider. Therefore, the warm-up

time may include a certain amount of error if there is any fluctuation of the oscillation frequency

when STOP mode is released. Thus, the warm-up time must be considered as an approximate

value.

Table 2-2 Warm-up Time Example (at fc = 16.0 MHz, fs = 32.768 kHz)

WUT

Warm-up Time [ms]

Return to NORMAL Mode

Return to SLOW Mode

12.288

4.096

3.072

1.024

750

250

5.85

1.95

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