X25128
be low when HOLD is first pulled low and SCK must
also be low when HOLD is released.
The HOLD input may be tied high either directly to V
CC
or tied to V
CC
through a resistor.
Operational Notes
The X25128 powers-up in the following state:
• The device is in the low power standby state.
• A high to low transition on CS is required to enter an
active state and receive an instruction.
• SO pin is high impedance.
• The “write enable” latch is reset.
Figure 1. Read E
2
PROM Array Operation Sequence
CS
Data Protection
The following circuitry has been included to prevent
inadvertent writes:
• The “write enable” latch is reset upon power-up.
• A WREN instruction must be issued to set the “write
enable” latch.
• CS must come high at the proper clock count in
order to start a write cycle.
0
SCK
1
2
3
4
5
6
7
8
9
10
20 21 22 23 24 25 26 27 28 29 30
INSTRUCTION
SI
16 BIT ADDRESS
15 14 13
3
2
1
0
DATA OUT
HIGH IMPEDANCE
SO
7
MSB
6
5
4
3
2
1
0
3091 FM F03
Figure 2. Read Status Register Operation Sequence
CS
0
SCK
1
2
3
4
5
6
7
8
9
10 11 12 13 14
INSTRUCTION
SI
DATA OUT
HIGH IMPEDANCE
SO
7
MSB
6
5
4
3
2
1
0
3091 FM F04
5
ICMIC [ IC MICROSYSTEMS ]
