TMPR3911 datasheet(263/462 Pages) TOSHIBA

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Chapter 12 Power Module

12-7

12.2.3

Power Down

A state transition into the Suspend State is called ‘Power Down’. Typically this is triggered by assertion

of the ONBUTN signal to power off the system. In the Suspend State VSTANDBY and VCCDRAM are

powered but VCC3 is not powered. Some system may have some other power supply lines which are

powered during the Suspend State. For example a system may supply power to a PC Card during the

Suspend State.

If the system is powered up and the PWROK signal is deasserted, the system must be powered down as

quickly as possible to preserve the contents of DRAM and/or SDRAM. All power supply lines, which are

not required to preserve valuable data, must be powered off. This state is called the Battery Backup State.

The system is powered down by software in the following sequence.

All modules in the TMPR3911/12 are disabled and all clocks in the Clock Module are turned

off.

The interrupts for the wake-up events such as power switch, alarm (RTC), and serial DCD are

enabled, and the other interrupts are disabled.

When the PWROK signal is deasserted, some system may disable all interrupts to prevent

unexpected power up after power will be supplied again.

The MEMPOWERDOWN bit in the Memory Configuration 4 Register is set in order to set the

DRAM and/or SDRAM into self-refresh mode. The following instructions must be executed

from cache memory. See Section 0 for more details.

By clearing the PWRCS and VCCON bits in the Power Control Register simultaneously the

PWRCS signal is deasserted. After the PWRCS is deasserted, the System Power Supply shuts

down VCC3 power line. Clearing VCCON bit results in negating ENSYSCLK and stopping all

internal clocks except 32kHz clock.

A wait loop for a few milliseconds follows. A few instructions may be executed before power off. The

rest of the wait loop is executed after the next power up to guarantee that some devices in the system are

stable after power up.

TMPR3911 Datasheet(PDF) 263 Page - Toshiba Semiconductor