1 5
RM25C128DS
DS-RM25C128DS–126B–11/2016
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.
To test if the device is in Ultra-Deep Power-Down mode without risk of bringing it out of Ultra-Deep Power-Down mode,
use the Read Status Register Byte 1 instruction. The UDPD bit in Status Register Byte 1 will be 1 (pulled high by the
internal pull-up resistor) if the device is in Ultra-Deep Power-Down mode, 0 otherwise.
Only the Exit Ultra-Deep Power-Down signal sequences described in Section 10.15 will bring the device out of the Ultra-
Deep Power-Down mode.
9.3 Auto Ultra-Deep Power-Down Mode after Write Operation
The Auto Ultra-Deep Power-Down Mode after Write Operation allows the device to further reduce its energy
consumption by automatically entering the Ultra-Deep Power-Down Mode after completing an internally timed Write
operation. The operation can be any one of the commands WR (Write), or WRSR (Write Status Register). Note that the
WRSR2 command does not cause the device to go into Ultra-Deep Power-Down Mode.
Only the Exit Ultra-Deep Power-Down signal sequences described in Section 10.15 will bring the device out of the Ultra-
Deep Power-Down Mode.
9.4 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.
9.5 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.