ACE25AB400G

Serial NOR Flash Memory 4M bits 3.0V Dual I/O Serial Flash Memory with 4KB Uniform Sector

VER 1.1

22

Read Identification (RDID) (9FH)

The Read Identification (RDID) command allows the 8-bit manufacturer identification to be read, followed

by two bytes of device identification. The device identification indicates the memory type in the first byte,

and the memory capacity of the device in the second byte. Any Read Identification (RDID) command

while an Erase or Program cycle is in progress, is not decoded, and has no effect on the cycle that is in

progress. The Read identification (RDID)command should not be issued while the device is in Deep

Power-Down Mode.

The device is first selected by driving CS# to low. Then, the 8-bit command code for the command is

shifted in. This is followed by the 24-bit device identification, stored in the memory, being shifted out on

Serial Data Output, each bit being shifted out during the falling edge of Serial Clock. The command

sequence is shown in Figure19. The Read Identification (RDID) command is terminated by driving CS# to

high at any time during data output. When CS# is driven high, the device is put in the Standby Mode.

Once in the Standby Mode, the device waits to be selected, so that it can receive, decode and execute

commands.

Read Unique ID (4BH)

The Read Unique ID command accesses a factory-set read-only 128bit number that is unique to each

ACE25AB400G device. The Unique ID can be used in conjunction with user software methods to help

prevent copying or cloning of a system. The Read Unique ID command sequence: CS# goes low→

sending Read Unique ID command→00H→00H→0H→128bit Unique ID Out→CS# goes high.

The command sequence is show below.

Figure19. Read Identification ID Sequence Diagram

Figure20 Read Unique ID (RUID) Sequence (Command 4B)