HN58X25128I/HN58X25256I

Rev.3.00, Jul.06.2005, page 8 of 20

Pin Function

Serial data output (Q)

This output signal is used to transfer data serially out of the device. Data is shifted out on the falling edge of serial

clock (C).

Serial data input (D)

This input signal is used to transfer data serially into the device. It receives instructions, addresses, and the data to be

written. Values are latched on the rising edge of serial clock (C).

Serial clock (C)

This input signal provides the timing of the serial interface. Instructions, addresses, or data present at serial data input

(D) are latched on the rising edge of serial clock (C). Data on serial data output (Q) changes after the falling edge of

serial clock (C).

Chip select (

S)

When this input signal is high, the device is deselected and serial data output (Q) is at high impedance. Unless an

internal write cycle is in progress, the device will be in the standby mode. Driving chip select (

S) low enables the

device, placing it in the active power mode. After power-up, a falling edge on chip select (

S) is required prior to the

start of any instruction.

Hold (

HOLD)

The hold (

HOLD) signal is used to pause any serial communications with the device without deselecting the device.

During the hold condition, the serial data output (Q) is high impedance, and serial data input (D) and serial clock (C)

are don’t care. To start the hold condition, the device must be selected, with chip select (

S) driven low.

Write protect (

W)

The main purpose of this input signal is to freeze the size of the area of memory that is protected against write

instructions (as specified by the values in the BP1 and BP0 bits of the status register). This pin must be driven either

high or low, and must be stable during all write operations.