25AA512 datasheet(20/36 Pages) MICROCHIP

20 / 36 page

25AA512

DS22021F-page 20

 2010 Microchip Technology Inc.

3.0

PIN DESCRIPTIONS

The descriptions of the pins are listed in Table 3-1.

TABLE 3-1:

PIN FUNCTION TABLE

3.1

Chip Select (CS)

A low level on this pin selects the device. A high level

deselects the device and forces it into Standby mode.

However, a programming cycle which is already

initiated or in progress will be completed, regardless of

the CS input signal. If CS is brought high during a

program cycle, the device will go into Standby mode as

soon as the programming cycle is complete. When the

device is deselected, SO goes to the high-impedance

state, allowing multiple parts to share the same SPI

bus. A low-to-high transition on CS after a valid write

sequence initiates an internal write cycle. After power-

up, a low level on CS is required prior to any sequence

being initiated.

3.2

Serial Output (SO)

The SO pin is used to transfer data out of the 25AA512.

During a read cycle, data is shifted out on this pin after

the falling edge of the serial clock.

3.3

Write-Protect (WP)

This pin is used in conjunction with the WPEN bit in the

STATUS register to prohibit writes to the nonvolatile

bits in the STATUS register. When WP is low and

WPEN is high, writing to the nonvolatile bits in the

STATUS register is disabled. All other operations

function normally. When WP is high, all functions,

including writes to the nonvolatile bits in the STATUS

low during a STATUS register write sequence will

disable writing to the STATUS register. If an internal

write cycle has already begun, WP going low will have

no effect on the write.

The WP pin function is blocked when the WPEN bit in

the STATUS register is low. This allows the user to

install the 25AA512 in a system with WP pin grounded

and still be able to write to the STATUS register. The

WP pin functions will be enabled when the WPEN bit is

set high.

3.4

Serial Input (SI)

The SI pin is used to transfer data into the device. It

receives instructions, addresses and data. Data is

latched on the rising edge of the serial clock.

3.5

Serial Clock (SCK)

The SCK is used to synchronize the communication

between a master and the 25AA512. Instructions,

addresses or data present on the SI pin are latched on

the rising edge of the clock input, while data on the SO

pin is updated after the falling edge of the clock input.

3.6

Hold (HOLD)

The HOLD pin is used to suspend transmission to the

25AA512 while in the middle of a serial sequence with-

out having to re-transmit the entire sequence over

again. It must be held high any time this function is not

being used. Once the device is selected and a serial

sequence is underway, the HOLD pin may be pulled

low to pause further serial communication without

resetting the serial sequence.

The HOLD pin should be brought low while SCK is low,

otherwise the HOLD function will not be invoked until

the next SCK high-to-low transition. The 25AA512 must

remain selected during this sequence. The SI and SCK

levels are “don’t cares” during the time the device is

paused and any transitions on these pins will be

ignored. To resume serial communication, HOLD

should be brought high while the SCK pin is low, other-

wise serial communication will not be resumed until the

next SCK high-to-low transition.

The SO line will tri-state immediately upon a high-to-

low transition of the HOLD pin, and will begin outputting

again immediately upon a subsequent low-to-high

transition of the HOLD pin, independent of the state of

SCK.

Name

Pin Number

Function

Chip Select Input

Serial Data Output

Write-Protect Pin

VSS

Ground

Serial Data Input

SCK

Serial Clock Input

HOLD

Hold Input

VCC

Supply Voltage

25AA512 Datasheet(PDF) 20 Page - Microchip Technology

25AA512 Datasheet(HTML) 20 Page - Microchip Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

Datasheet Download

Link URL