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5167E–SFLSH–5/09

AT25FS010

2. Serial Interface Description

MASTER: The device that generates the serial clock.

SLAVE: Because the Serial Clock pin (SCK) is always an input, the AT25FS010 always oper-

ates as a slave.

TRANSMITTER/RECEIVER: The AT25FS010 has separate pins designated for data transmis-

sion (SO) and reception (SI).

MSB: The Most Significant Bit (MSB) is the first bit transmitted and received.

SERIAL OP-CODE: After the device is selected with CS going low, the first byte will be

received. This byte contains the op-code that defines the operations to be performed.

INVALID OP-CODE: If an invalid op-code is received, no data will be shifted into the

AT25FS010, and the serial output pin (SO) will remain in a high impedance state until the falling

edge of CS is detected again. This will reinitialize the serial communication.

CHIP SELECT: The AT25FS010 is selected when the CS pin is low. When the device is not

selected, data will not be accepted via the SI pin, and the serial output pin (SO) will remain in a

high impedance state.

HOLD: The HOLD pin is used in conjunction with the CS pin to select the AT25FS010. When

the device is selected and a serial sequence is underway, HOLD can be used to pause the serial

communication with the master device without resetting the serial sequence. To pause, the

HOLD pin must be brought low while the SCK pin is low. To resume serial communication, the

HOLD pin is brought high while the SCK pin is low (SCK may still toggle during HOLD). Inputs to

the SI pin will be ignored while the SO pin is in the high impedance state.

WRITE PROTECT: The AT25FS010 has a write lockout feature that can be activated by assert-

ing the write protect pin (WP). When the lockout feature is activated, locked-out sectors will be

READ only. The write protect pin will allow normal read/write operations when held high. When

the WP is brought low and WPEN bit is “1”, all write operations to the status register are inhib-

ited. WP going low while CS is still low will interrupt a write to the status register. If the internal

status register 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 “0”. This will allow the user to install the AT25FS010 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 “1”.