DS1847

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The master must terminate the write cycle with a STOP condition or the data clocked into the DS1847

will not be latched into permanent memory.

Acknowledge Polling: Once the internally-timed write has started and the DS1847 inputs are disabled,

acknowledge polling can be initiated. The process involves transmitting a START condition followed by

the device address. The R/W bit signifies the type of operation that is desired. The read or write sequence

will only be allowed to proceed if the internal write cycle has completed and the DS1847 responds with a

zero.

Read Operations: After receiving a matching address byte with the R/W bit set high, the device goes

into the read mode of operation. There are three read operations: current address read, random read, and

sequential address read.

CURRENT ADDRESS READ

The DS1847 has an internal address register that maintains the address used during the last read or write

was the last byte in memory, then the register resets to the first address. This address stays valid between

operations as long as power is available.

Once the device address is clocked in and acknowledged by the DS1847 with the R/W bit set to high, the

current address data word is clocked out. The master does not respond with a zero, but does generate a

STOP condition afterwards.

RANDOM READ

A random read requires a dummy byte write sequence to load in the data word address. Once the device

and data address bytes are clocked in by the master and acknowledged by the DS1847, the master must

generate another START condition. The master now initiates a current address read by sending the device

address with the read/write bit set high. The DS1847 will acknowledge the device address and serially

clocks out the data byte.

SEQUENTIAL ADDRESS READ

Sequential reads are initiated by either a current address read or a random address read. After the master

receives the first data byte, the master responds with an acknowledge. As long as the DS1847 receives

this acknowledge after a byte is read, the master may clock out additional data words from the DS1847.

After reaching address FFh, it resets to address 00h.

The sequential read operation is terminated when the master initiates a stop condition. The master does

not respond with a zero.

For a more detailed description of 2-wire theory of operation, refer to the next section.