DESIGN OF A CUSTOM ASIC INCORPORATING CAN™ AND 1 ...

A data access instruction may be one of the following: WRITE_SP (0x0F), READ_SP
(0xAA), COPY_SP (0x55), and READ_MEM (0xF0).
WRITE_SP – The Write Scratchpad command applies to the data memory and the
writeable addresses in the register page of 1 – Wire® slave devices. After issuing the
Write Scratchpad command, the bus master must provide a 2-byte target address
followed by the data to be written to the scratchpad.
READ_SP – The Read Scratchpad command allows the 1 – Wire® Master to read the
contents of the scratchpad. The data transfer starts with the least significant bit of byte 0
and continues through the scratchpad until the ninth byte (byte 8 – CRC) is read. The 1 –
Wire® Master may issue a reset to terminate at any time if only part of the scratchpad
data is needed.
COPY_SP – The Copy Scratchpad command is used to copy data from the scratchpad of
the slave device to the memory of the slave device. After issuing the copy scratchpad
command, the master must provide a 3-byte authorization pattern which is obtained by
reading the scratchpad for verification.
READ_MEM – The Read Memory command is used to read data from 1 – Wire® slave
devices that support EEPROM. The bus master follows the command byte with a two
byte address that indicates a starting byte location within the EEPROM data field. With
every subsequent read data time slot, the bus master receives data starting at the initial
address and continuing until the end of the EEPROM data field is reached or until a Reset
Pulse is issued.
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