Most CryptoMemory® commands have the same format as a Two-Wire Interface
(TWI) write command, characterized by a zero in the LSB of the first byte (device address).
The number of word address bytes in a TWI write command will vary depending on the size of the
memory being addressed. All bytes, whether part of the command or data, are generated by the
host and sent to the memory device, which will acknowledge each byte.Figure 7-2. TWI Write Command
All CryptoMemory commands have a zero in the LSB of the first byte. All CryptoMemory commands use
four bytes to define the command and address the memory. All CryptoMemory commands, except for
the read commands, send an additional 0 to 128 bytes of data following the four command bytes.
These commands comply with the format of a TWI write command.
The CryptoMemory read commands (Read User Zone, System Read) do not comply with the format of a
TWI write or read command. The CryptoMemory read command resembles a TWI write command (LSB of
the first byte = 0), but after the fourth byte of the command, the CryptoMemory device begins
to send data back on the bus. The number of bytes sent by CryptoMemory will be equal to the
value of N.Figure 7-3. CryptoMemory®
Read Command
The response from CryptoMemory will cause contention with the host on a standard TWI bus.
Typically CryptoMemory cannot be used on a standard TWI bus and requires a modified TWI
protocol to account for its unique read command format.
The online versions of the documents are provided as a courtesy. Verify all content and data in the device’s PDF documentation found on the device product page.
