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DS1992/DS1993/DS1994
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102199
Copy Scratchpad [55h]
This command is used to copy data from the scratchpad to memory. After issuing the copy scratchpad
command, the user must provide a 3-byte authorization pattern. This pattern must exactly match the data
contained in the three address registers (TA1, TA2, E/S, in that order). If the pattern matches, the AA
(Authorization Accepted) flag will be set and the copy will begin. A logic 0 will be transmitted after the
data has been copied until a reset pulse is issued by the user. Any attempt to reset the part will be ignored
while the copy is in progress. Copy typically takes 30
s.
The data to be copied is determined by the three address registers. The scratchpad data from the
beginning offset through the ending offset, will be copied to memory, starting at the target address.
Anywhere from 1 to 32 bytes may be copied to memory with this command. Whole bytes are copied even
if only partially written. The AA flag will be cleared only by executing a write scratchpad command.
Read Memory [F0h]
The read memory command may be used to read the entire memory. After issuing the command, the user
must provide the 2-byte target address. After the two bytes, the user reads data beginning from the target
address and may continue until the end of memory, at which point logic 1’s will be read. It is important to
realize that the target address registers will contain the address provided. The ending offset/data status
byte is unaffected.
The hardware of the DS1992/DS1993/DS1994 provides a means to accomplish error–free writing to the
memory section. To safeguard reading data in the 1–Wire environment and to simultaneously speed up
data transfers, it is recommended to packetize data into data packets of the size of one memory page each.
Such a packet would typically store a 16–bit CRC with each page of data to ensure rapid, error–free data
transfers that eliminate having to read a page multiple times to determine if the received data is correct or
not. (See the Book of DS19xx iButton Standards, Chapter 7 for the recommended file structure to be used
with the 1–Wire environment.)