Shanghai Belling Corp., Ltd

BL24C128/256

6

C

URRENT ADDRESS READ: The internal data word address counter maintains the last address

accessed during the last read or write operation, incremented by one. This address stays valid between

operations as long as the chip power is maintained. The address “roll over” during read is from the last

byte of the last memory page to the first byte of the first page. The address “roll over” during write is from

the last byte of the current page to the first byte of the same page.

Once the device address with the read/write select bit set to “1” is clocked in and acknowledged by the

EEPROM, the current address data word is serially clocked out. The microcontroller does not respond

with an input “0” but does generate a following stop condition (see

Figure

7).

RANDOM READ: A random read requires a “dummy” byte write sequence to load in the data word

address. Once the device address word and data word address are clocked in and acknowledged by the

EEPROM, the microcontroller must generate another start condition. The microcontroller now initiates a

current address read by sending a device address with the read/write select bit high. The EEPROM

acknowledges the device address and serially clocks out the data word. The microcontroller does not

respond with a “0” but does generate a following stop condition (see Figure 9).

SEQUENTIAL READ: Sequential reads are initiated by either a current address read or a random

address read. After the microcontroller receives a data word, it responds with an acknowledge. As long

as the EEPROM receives an acknowledge, it will continue to increment the data word address and

serially clock out sequential data words. When the memory address limit is reached, the data word

address will “roll over” and the sequential read will continue.

The sequential read operation is

terminated when the microcontroller does not respond with a “0” but does generate a following stop

condition (see

Figure

10)

Figure 4.

Device Address

Figure 5.

Byte Write

Figure 6.

Page Write