AT24CS128/256

8

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

zero but does generate a following stop condition (refer to

Figure 5).

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 con-

tinue. The sequential read operation is terminated when

the microcontroller does not respond with a zero but does

generate a following stop condition (refer to Figure 6).

Figure 1. Device Address

Figure 2. Byte Write

Figure 3. Page Write

(* = DON’T CARE bit)

(† = DON’T CARE bit for the 128K)