24C64 datasheet(4/8 Pages) ETC

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24C64

DEVICE ADDRESSING:

Following the start condition, the master will issue a device

address byte consisting of 1010 (A2) (A1) (A0) (R/W) to ac-

cess the selected Turbo IC 24C64 for a read or write opera-

tion. The A[2:0] bits must match with the address input pins

of the selected Turbo IC 24C64. If there is a match, the se-

lected Turbo IC 24C64 acknowledges during the ninth clock

cycle by pulling the SDA bus low. If there is no match, the

Turbo IC 24C64 does not acknowledge during the ninth clock

cycle and goes into standby mode. The (R/W) bit is a high (1)

for read and low (0) for write.

DATA INPUT DURING WRITE OPERATION:

During the write operation, the Turbo IC 24C64 latches the

SDA bus signal on the rising edge of the SCL clock.

DATA OUTPUT DURING READ OPERATION:

During the read operation, the Turbo IC 24C64 serially shifts

the data onto the SDA bus on the falling edge of the SCL

clock.

MEMORY ADDRESSING:

The memory address is sent by the master in the form of 2

memory address bytes. The memory address bytes can only

be sent as part of a write operation. The most significant

address byte XXX (B12) (B11) (B10) (B9) (B8) is sent first,

where X represents “don’t care”. Then the least significant

address byte (B7) (B6) (B5) (B4) (B3) (B2) (B1) (B0) is sent

last.

BYTE WRITE OPERATION:

The master initiates the byte write operation by issuing a

start condition, followed by the device address byte 1010

(A2) (A1) (A0) 0, followed by 2 memory address bytes, fol-

lowed by one data byte, followed by an acknowledge, then a

stop condition. After each byte transfer, the Turbo IC 24C64

acknowledges the successful data transmission by pulling

the SDA bus low. The stop condition starts the internal

EEPROM write cycle, and all inputs are disabled until the

completion of the write cycle. If the WP pin is high (1) and the

memory address is within the upper quadrant (1800-1FFFH)

of memory, then the stop condition does not start the inter-

nal write cycle and the Turbo IC 24C64 is immediately ready

for the next command.

PAGE WRITE OPERATION:

The master initiates the page write operation by issuing a

start condition, followed by the device address byte 1010

(A2) (A1) (A0) 0, followed by 2 memory address bytes, fol-

lowed by up to 32 data bytes, followed by an acknowledge,

then a stop condition. After each byte transfer, the Turbo

IC24C64 acknowledges the successful data transmission by

pulling SDA low. After each data byte transfer, the memory

address counter is automatically incremented by one. The

stop condition starts the internal EEPROM write cycle only if

the stop condition occurs in the clock cycle immediately fol-

lowing the acknowledge (10th clock cycle). All inputs are dis-

abled until the completion of the write cycle. If the WP pin is

high (1) and the memory address is within the upper quad-

rant (1800-1FFFH) of memory, then the stop condition does

not start the internal write cycle, and the Turbo IC 24C64 is

immediately ready for the next command.

POLLING ACKNOWLEDGE:

During the internal write cycle of a write operation in the Turbo

IC 24C64, the completion of the write cycle can be detected

by polling acknowledge. The master starts acknowledge poll-

ing by issuing a start condition, then followed by the device

address byte 1010 (A2) (A1) (A0) 0. If the internal write cycle

is finished, the Turbo IC 24C64 acknowledges by pulling the

SDA bus low. If the internal write cycle is still ongoing, the

Turbo IC 24C64 does not acknowledge because it’s inputs

are disabled. Therefore, the device will not respond to any

command. By using polling acknowledge, the system delay

for write operations can be reduced. Otherwise, the system

needs to wait for the maximum internal write cycle time, tWC,

given in the spec.

POWER ON RESET:

The Turbo IC 24C64 has a Power On Reset circuit (POR) to

prevent data corruption and accidental write operations dur-

ing power up. On power up, the internal reset signal is on

and the Turbo IC 24C64 will not respond to any command

until the VCC voltage has reached the POR threshold value.

Turbo IC, Inc.

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