ACE25C400 Datasheet, PDF (20/31 Pages) ACE Technology Co., LTD. – 4MB Serial Flash Memory

ACE25C400
4MB Serial Flash Memory
Power-down (B9h)
Although the standby current during normal operation is relatively low, standby current can be further
reduced with the Power-down instruction. The lower power consumption makes the Power-down
instruction especially useful for battery powered applications (See I_CC1 and I_CC2 in “12.6 AC Electrical
Characteristics”). The instruction is initiated by driving the CS# pin low and shifting the instruction
code “B9h” as shown in Figure 18.
The CS# pin must be driven high after the eighth bit has been latched. If t his is not done the
Power-down instruction will not be executed. After CS# is driven high, the power-down state will enter
within the time duration of t_DP (See “12.6 AC Electrical Characteristics”). While in the power-down
state only the Release from Power- down / Device ID instruction, which restores the device to normal
operation, will be recognized. All other instructions are ignored. This includes the Read Status
Register instruction, which is always available during normal operation. Ignoring all but o ne
instruction makes the Power Down state a useful condition for securing maximum write protection.
The device always powers-up in the normal operation with the standby current of I_CC1.
Figure 18 Deep power-down instruction
Release Power-down / Device ID (ABh)
The Release from Power-down / Device ID instruction is a multi-purpose instruction. It can be used
to release the device from the power-down state, or obtain the devices electronic identification (ID)
number.
To release the device from the power-down state, the instruction is issued by driving the CS# pin low,
shifting the instruction code “ABh” and driving CS# high as shown in Figure 19. Release from
power-down will take the time duration of tRES1 (See “12.6 AC Electrical Characteristic s”) before the
device will resume normal operation and other instructions are accepted. The CS# pin must remain
high during the tRES1 time duration.
When used only to obtain the Device ID while not in the power-down state, the instruction is initiated
by driving the CS# pin low and shifting the instruction code “ABh” followed by 3-dummy bytes. The
Device ID bits are then shifted out on the falling edge of CLK with most significant bit (MSB) first as
shown in Figure 19. The Device ID value for the ACE25C400 is listed in Table 3 Manufacturer and
Device Identification table. The Device ID can be read continuously. The instruction is completed by
driving CS# high.
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