M45PE20 Datasheet, PDF (15/35 Pages) STMicroelectronics – 2 Mbit, Low Voltage, Page-Erasable Serial Flash Memory With Byte-Alterability and a 25 MHz SPI Bus Interface

M45PE20
Read Data Bytes (READ)
The device is first selected by driving Chip Select
(S) Low. The instruction code for the Read Data
Bytes (READ) instruction is followed by a 3-byte
address (A23-A0), each bit being latched-in during
the rising edge of Serial Clock (C). Then the mem-
ory contents, at that address, is shifted out on Se-
rial Data Output (Q), each bit being shifted out, at
a maximum frequency f_R, during the falling edge of
Serial Clock (C).
The instruction sequence is shown in Figure 11..
The first byte addressed can be at any location.
The address is automatically incremented to the
next higher address after each byte of data is shift-
ed out. The whole memory can, therefore, be read
with a single Read Data Bytes (READ) instruction.
When the highest address is reached, the address
counter rolls over to 000000h, allowing the read
sequence to be continued indefinitely.
The Read Data Bytes (READ) instruction is termi-
nated by driving Chip Select (S) High. Chip Select
(S) can be driven High at any time during data out-
put. Any Read Data Bytes (READ) instruction,
while an Erase, Program or Write cycle is in
progress, is rejected without having any effects on
the cycle that is in progress.
Figure 11. Read Data Bytes (READ) Instruction Sequence and Data-Out Sequence
S
0 1 2 3 4 5 6 7 8 9 10 28 29 30 31 32 33 34 35 36 37 38 39
C
Instruction
24-Bit Address
D
23 22 21 3 2 1 0
MSB
High Impedance
Q
Data Out 1
Data Out 2
76543 2107
MSB
AI03748D
Note: Address bits A23 to A18 are Don’t Care.
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