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RM25C512C
DS-RM25C512C–079A–03/2016
8.3.2 Ultra-Deep Power Down mode
The Ultra-Deep Power Down mode allows the device to further reduce its energy consumption compared to the existing
Standby and Power Down modes by shutting down additional internal circuitry. The UDPD command is used to instruct
the device to enter Ultra-Deep Power Down mode.
When the device is in the Ultra-Deep Power Down mode, all commands including the Read Status Register and Resume
From Power Down commands will be ignored. Since all commands will be ignored, the mode can be used as an extra
protection mechanism against inadvertent or unintentional program and erase operations.
Only the Exit Ultra-Deep Power Down signal sequences described in section 8-13 will bring the device out of the Ultra-
Deep Power Down mode.
8.3.3 Auto Power Down Enable.
For frequencies lower than fAPD (see AC Operating Characteristics), the APDE bit in the Status Register may be enabled.
The device will then automatically enter Power Down mode instead of Standby mode when idle. (CS is high, no Write or
Erase operation in progress).
In this mode, the device will behave normally to all commands, and will leave Power Down mode once CS is pulled down.
If Auto Power Down is enabled, and the SCK Clock Frequency is increased to a speed higher than fAPD, the device may
not react as expected to the command. Before changing SCK frequency, the APDE bit in the Status Register must be
disabled.
Note that the PD or UDPD commands may still be used as additional software write protection features when Auto Power
Down is enabled. Note that if the PD command is issued while Auto Power Down is enabled, the device will enter Power
Down mode, and all instructions given will be ignored except the Resume From Power Down (RES) instruction. The
device will not wake up immediately after CS is pulled down.
8.3.4 Low Power Standby Enable.
For frequencies lower than fAPD (see AC Operating Characteristics), the LPSE bit in the Status Register may be enabled.
The device will then automatically enter Low Power Standby mode when idle. (CS is high, no Write or Erase operation in
progress).
In this mode, the device will behave normally to all commands, and will leave Low Power Standby mode once CS is
pulled down.
If Low Power Standby Mode is enabled, and the SCK Clock Frequency is increased to a speed higher than fAPD, the
device may not react as expected to the command. Before changing SCK frequency, the LPSE bit in the Status Register
must be disabled.
Note that the PD or UDPD commands may still be used as additional software write protection features when Low Power
Standby Mode is enabled. Note that if the PD command is issued while Low Power Standby Mode is enabled, the device
will enter Power Down mode, and all instructions given will be ignored except the Resume From Power Down (RES)
instruction. The device will not wake up immediately after CS is pulled down.
9. Command Descriptions
9.1 WREN (Write Enable):
The device powers up with the Write Enable Latch set to zero. This means that no write or erase instructions can be
executed until the Write Enable Latch is set using the Write Enable (WREN) instruction. The Write Enable Latch is also
set to zero automatically after any non-read instruction. Therefore, all page programming instructions and erase
instructions must be preceded by a Write Enable (WREN) instruction. The sequence for the Write Enable instruction is
shown in Figure 9-1.