M25P20
Instructions
6.3
Read Identification (RDID)
The Read Identification (RDID) instruction is available in products with Process Technology
code X only.
The Read Identification (RDID) instruction allows the 8-bit manufacturer identification to be
read, followed by two bytes of device identification. The manufacturer identification is
assigned by JEDEC, and has the value 20h for Numonyx. The device identification is
assigned by the device manufacturer, and indicates the memory type in the first byte (20h),
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 Read Identification (RDID) instruction should not be issued while the device is in Deep
Power-down mode.
The device is first selected by driving Chip Select (S) Low. Then, the 8-bit instruction code
for the instruction 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 being shifted out during
the falling edge of Serial Clock (C).
The instruction sequence is shown in Figure 9.
The Read Identification (RDID) instruction is terminated 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 Stand-by Power mode. Once in
the Stand-by Power mode, the device waits to be selected, so that it can receive, decode
and execute instructions.
Table 5.
Read Identification (RDID) Data-Out Sequence
Device Identification
Manufacturer Identification
Memory Type
Memory Capacity
20h
20h
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 17 18
28 29 30 31
C
D
Instruction
Manufacturer Identification
Device Identification
High Impedance
Q
15 14 13
MSB
3
2
1
0
MSB
AI06809b
19/50
NUMONYX [ NUMONYX B.V ]
