AT25128B/AT25256B
Pin Description
2.
Pin Description
The descriptions of the pins are listed in Table 2-1.
Table 2-1.ꢀPin Function Table
(1)
Name
CS
8-Lead SOIC
8-Lead TSSOP
8-Pad UDFN
8-Ball VFBGA Function
1
2
3
4
5
6
7
8
1
2
3
4
5
6
7
8
1
2
3
4
5
6
7
8
1
2
3
4
5
6
7
8
Chip Select
SO
Serial Data Output
Write-Protect
(2)
WP
GND
SI
Ground
Serial Data Input
Serial Data Clock
Suspends Serial Input
Device Power Supply
SCK
(2)
HOLD
V
CC
Note:ꢀ
1. The exposed pad on this package can be connected to GND or left floating.
2. The Write-Protect (WP) and Hold (HOLD) pins should be driven high or low as appropriate.
2.1
Chip Select (CS)
The AT25128B/AT25256B is selected when the Chip Select (CS) pin is low. When the device is not
selected, data will not be accepted via the Serial Data Input (SI) pin, and the Serial Output (SO) pin will
remain in a high-impedance state.
To ensure robust operation, the CS pin should follow VCC upon power-up. It is therefore recommended to
connect CS to VCC using a pull-up resistor (less than or equal to 10 kΩ). After power-up, a low level on
CS is required prior to any sequence being initiated.
2.2
2.3
Serial Data Output (SO)
The Serial Data Output (SO) pin is used to transfer data out of the AT25128B/AT25256B. During a read
sequence, data is shifted out on this pin after the falling edge of the Serial Data Clock (SCK).
Write-Protect (WP)
The Write-Protect (WP) pin will allow normal read/write operations when held high. When the WP pin is
brought low and WPEN bit is set to a logic ‘1’, all write operations to the STATUS register are inhibited.
WP going low while CS is still low will interrupt a write operation to the STATUS register. If the internal
write cycle has already been initiated, WP going low will have no effect on any write operation to the
STATUS register. The WP pin function is blocked when the WPEN bit in the STATUS register is set to a
logic ‘0’. This will allow the user to install the AT25128B/AT25256B in a system with the WP pin tied to
ground and still be able to write to the STATUS register. All WP pin functions are enabled when the
WPEN bit is set to a logic ‘1’.
2.4
Ground (GND)
The ground reference for the Device Power Supply (VCC). The Ground (GND) pin should be connected to
the system ground.
DS20006193A-page 5
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