The Random Read command provides the host with the ability to sequentially clock data from the
device, starting from a specified address. The host needs to issue a “dummy” write operation
to specify the start address for the Random Read. The host does this by clocking in the four
bytes of the write command and then following them with a Start condition instead of a data
byte. At this point, the device’s internal logic is pointing to the address from the aborted
write operation. The host may then issue the Random Read command byte ($B1), to which the
device will respond with the EEPROM byte at the current address location and then increment
the internal address by one. The device will continue to sequentially send out bytes as long
as the host keeps acknowledging each byte with an ACK. Address rollover occurs from the last
byte of the current zone to the first byte of that zone. The host terminates the Random Read
by issuing a NACK signal instead of an ACK.Figure 8-4. Random Read Command
CryptoMemory® will NACK the N parameter of the dummy write operation if the
write is issued to an illegal write location. The NACK response, however, does not affect the
loading of the read address. The Random Read command works for both configuration and user
memory. It is important to implement the CryptoMemory read commands as specified; otherwise,
CryptoMemory responses will cause contention on the bus with a host using the standard TWI
protocol.
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.
