Datasheet

DS1920
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MEMORY AND CONTROL FUNCTION COMMANDS
The following command protocols are summarized in Table 2, and by the flowchart of Figure 9.
Write Scratchpad [4Eh]
This command writes to the scratchpad of the DS1920, starting at address 2. The next 2 bytes written will
be saved in scratchpad memory, at address locations 2 and 3. Writing may be terminated at any point by
issuing a reset. However, if a reset occurs before both bytes have been completely sent, the contents of
these bytes will be indeterminate. Bytes 2 and 3 can be read and written; all other bytes are read only.
Read Scratchpad [BEh]
This command reads the complete scratchpad. After the last byte of the scratchpad is read, the bus master
will receive an 8-bit CRC of all scratchpad bytes. If not all locations are to be read, the master may issue
a reset to terminate reading at any time.
Copy Scratchpad [48h]
This command copies from the scratchpad into the EEPROM of the DS1920, storing the temperature
trigger bytes in nonvolatile memory. The bus master has to enable a strong pullup for at least 10 ms
immediately after issuing this command.
Convert Temperature [44h]
This command begins a temperature conversion. No further data is required. The bus master has to enable
a strong pullup for 0.75 seconds immediately after issuing this command.
Recall [B8h]
This command recalls the temperature trigger values stored in EEPROM to the scratchpad. This recall
operation happens automatically upon power-up to the DS1920 as well, so valid data is available in the
scratchpad as soon as the device has power applied.