24C64
DEVICE ADDRESSING:
Following the start condition, the master will issue a device
address byte consisting of 1010 (A2) (A1) (A0) (R/W) to access the selected Turbo IC 24C64 for a read or write operation. The A[2:0] bits must match with the address input pins
of the selected Turbo IC 24C64. If there is a match, the selected Turbo IC 24C64 acknowledges during the ninth clock
cycle by pulling the SDA bus low. If there is no match, the
T urbo IC 24C64 does not ackno wledge 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 b us 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 OPERA TION:
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, followed by one data byte, f ollow ed by an ackno wledge, then a
stop condition. After each b yte transf er, 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 internal write cycle and the Turbo IC 24C64 is immediately ready
for the next command.
P AGE 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, followed 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 b y
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 following the acknowledge (10th cloc k cycle). 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 internal write cycle, and the Turbo IC 24C64 is
immediately ready for the next command.
POLLING ACKNO WLEDGE:
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 polling 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 dela y
for write operations can be reduced. Otherwise, the system
needs to wait for the maxim um 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 during 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 v oltage has reached the POR threshold value.
Turbo IC, Inc.
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