DS28E01-100+ Maxim Integrated, DS28E01-100+ Datasheet - Page 9

• Manufacturer Part Number: DS28E01-100+
• Description: EEPROM
• Manufacturer: Maxim Integrated

1Kb Protected 1-Wire EEPROM
with SHA-1 Engine
valued bit of the E/S register, called authorization
accepted (AA), acts as a flag to indicate that the data
stored in the scratchpad has already been copied to
the target memory address. Writing data to the scratch-
pad clears this flag.
To write data to the DS28E01-100, the scratchpad must
be used as intermediate storage. First, the master
issues the Write Scratchpad command, which specifies
the desired target address and the data to be written to
the scratchpad. Note that writes to data memory must
be performed on 8-byte boundaries with the three LSBs
of the target address T[2:0] equal to 000b. Therefore, if
T[2:0] are sent with nonzero values, the device sets
these bits to 0 and uses the modified address as the
target address. The master should always send eight
complete data bytes. After the 8 bytes of data have
been transmitted, the master can elect to receive an
inverted CRC-16 of the Write Scratchpad command,
the address as sent by the master, and the data as sent
by the master. The master can compare the CRC to the
value it has calculated itself to determine if the commu-
nication was successful. After the scratchpad has been
written, the master should always perform a Read
Scratchpad to verify that the intended data was in fact
written. During a Read Scratchpad, the DS28E01-100
repeats the target address TA1 and TA2 and sends the
contents of the E/S register. The partial flag (bit 5 of the
E/S register) is set to 1 if the last data byte the
DS28E01-100 received during a Write Scratchpad or
Refresh Scratchpad command was incomplete, or if
there was a loss of power since data was last written to
the scratchpad. The authorization-accepted (AA) flag
(bit 7 of the E/S register) is normally cleared by a Write
Scratchpad or Refresh Scratchpad; therefore, if it is set
to 1, it indicates that the DS28E01-100 did not under-
stand the proceeding Write (or Refresh) Scratchpad
command. In either of these cases, the master should
rewrite the scratchpad. After the master receives the
E/S register, the scratchpad data is received. The
descriptions of Write Scratchpad and Refresh
Scratchpad provide clarification of what changes can
occur to the scratchpad data under certain conditions.
An inverted CRC of the Read Scratchpad command,
target address, E/S register, and scratchpad data fol-
lows the scratchpad data. As with the Write Scratchpad
command, this CRC can be compared to the value the
master has calculated to determine if the communica-
tion was successful. After the master has verified the
DS28E01-100
10
Writing with Verification
ABRIDGED DATA SHEET
data, it can send the Copy Scratchpad to copy the
scratchpad to memory. Alternatively, the Load First
Secret or Compute Next Secret command can be
issued to change the secret. See the descriptions of
these commands for more information.
Refer to the full data sheet for this information.
Maxim Integrated