ACE24AC1024EDPTH datasheet(7/16 Pages) ACE

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ACE24AC1024E

Two-wire Serial EEPROM

VER 1.1

Read Operations

The read command is similar to the write command except the 8th read/write bit in address word is set to

“1”. The three read operation modes are described as follows:

(A)

Current Address Read

The EEPROM internal address word counter maintains the last read or write address plus one if the

power supply to the device has not been cut off. To initiate a current address read operation, the

micro- controller issues a start bit and a valid device address word with the read/write bit (8th) set to

“1”. The EEPROM will response with an acknowledge signal on the 9th serial clock cycle. An 8-bit

data word will then be serially clocked out. The internal address word counter will then automatically

increase by one.

For current address read the micro-controller will not issue an acknowledge signal

on the 18th clock cycle. The micro-controller issues a valid stop bit after the 18th clock cycle to

terminate the read operation.

The device then returns to standby mode (see Figure 5).

(B)

Sequential Read

The sequential read is very similar to current address read. The micro-controller issues a start bit

and a valid device address word with read/write bit (8th

) set to “1”. The EEPROM will response with

an acknowledge signal on the 9th serial clock cycle.

An 8-bit data word will then be serially clocked

out. Meanwhile the internally address word counter will then automatically increase by one.

Unlike current address read, the micro-controller sends an acknowledge signal on the 8th clock cycle

signaling the EEPROM device that it wants another byte of data. Upon receiving the acknowledge

signal, the EEPROM will serially clocked out an 8-bit data word based on the incremented internal

address counter. If the micro-controller needs another data, it sends out an acknowledge signal on

the 27th clock cycle. Another 8-bit data word will then be serially clocked out. This sequential read

continues as long as the micro-controller sends an acknowledge signal after receiving a new data

word. When the internal address counter reaches its maximum valid address, it rolls over to the

beginning of the memory array address. Similar to current address read, the micro- controller can

terminate the sequential read by not acknowledging the last data word received, but sending a stop

bit afterwards instead (figure 6).

(C)

Random Read

Random read is a two-steps process. The first step is to initialize the internal address counter with a

target read add

ress using a “dummy write” instruction. The second step is a current address read.

To initialize the internal address counter with a target read address, the micro-controller issues a

start bit first, follows by a valid device address with the read/write bit (8th

) set to “0”. The EEPROM

will then acknowledge. The micro-controller will then send two address words. Again the EEPROM

will acknowledge. Instead of sending a valid written data to the EEPROM, the micro-controller

performs a current address read instruction to read the data. Note that once a start bit is issued, the

EEPROM will reset the internal programming process and continue to execute the new instruction -

which is to read the current address (figure 7).

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