M45PE20 Datasheet, PDF (13/35 Pages) STMicroelectronics – 2 Mbit, Low Voltage, Page-Erasable Serial Flash Memory With Byte-Alterability and a 25 MHz SPI Bus Interface

M45PE20
Read Identification (RDID)
The Read Identification (RDID) instruction allows
the 8-bit manufacturer identification to be read, fol-
lowed by two bytes of device identification. The
manufacturer identification is assigned by JEDEC,
and has the value 20h for STMicroelectronics. The
device identification is assigned by the device
manufacturer, and indicates the memory type in
the first byte (40h), and the memory capacity of the
device in the second byte (12h).
Any Read Identification (RDID) instruction while
an Erase or Program cycle is in progress, is not
decoded, and has no effect on the cycle that is in
progress.
The device is first selected by driving Chip Select
(S) Low. Then, the 8-bit instruction code for the in-
struction is shifted in. This is followed by the 24-bit
device identification, stored in the memory, being
shifted out on Serial Data Output (Q), each bit be-
ing shifted out during the falling edge of Serial
Clock (C).
The instruction sequence is shown in Figure 9..
The Read Identification (RDID) instruction is termi-
nated by driving Chip Select (S) High at any time
during data output.
When Chip Select (S) is driven High, the device is
put in the Standby Power mode. Once in the
Standby Power mode, the device waits to be se-
lected, so that it can receive, decode and execute
instructions.
Table 5. Read Identification (RDID) Data-Out Sequence
Manufacturer Identification
Device Identification
Memory Type
Memory Capacity
20h
40h
12h
Figure 9. Read Identification (RDID) Instruction Sequence and Data-Out Sequence
S
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 16 18 28 29 30 31
C
Instruction
D
Manufacturer Identification
Device Identification
High Impedance
Q
15 14 13 3 2 1 0
MSB
MSB
AI06809
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