ACE24AC04 Datasheet, PDF (7/18 Pages) –

ACE24AC04.08.16
Two-wire Serial EEPROM
automatically increase by one. For current address read the micro-controller will not issue an
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acknowledge signal on the 18 clock cycle. The micro-controller issues a valid stop bit after the
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18 clock cycle to terminate the read operation. The device then returns to standby mode.
(B) Sequential Read
The sequential read is very similar to current address read. The micro-controller issues a start bit
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and a valid device address word with read/write bit (8 ) set to “1”. The EEPROM will response with
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an acknowledge signal on the 9 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 18th 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
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the 27 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.
(C) Random Read
Random read is a two-steps process. The first step is to initialize the internal address counter with a
target read address 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
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start bit first, follows by a valid device address with the read/write bit (8 ) set to “0”. The EEPROM
will then acknowledge. The micro-controller will then send the address word. 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 3: Byte Write Instruction (SDA Input)
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