6.5.3.7 OVERDRIVE MATCH ROM Command [69h]

The OVERDRIVE MATCH ROM command is used to select a specific responder device when there are

multiple responder devices on the SDQ bus, and sets the device into Overdrive mode at the same time.

The OVERDRIVE MATCH ROM command can also be used with a single responder device on the bus. The

responder device that matches the 64-bit serial ID is selected and available to perform subsequent memory

function commands in overdrive speed. Other responder devices that are already in Overdrive mode continue

to be in Overdrive mode until the host can bring all the responder devices back to standard speed by issuing a

reset pulse of at least 480 μs.

6.5.4 Memory Function Commands

6.5.4.1 Write Scratchpad Command [0Fh]

The Write Scratchpad command, 0Fh, is used to write to the scratchpad. After selecting the target TMF0008

using the ROM command, the host provides the 2-byte address followed by the data. The TMF0008 sets the 5

LSB bits of the 2-byte address as the scratchpad offset address. Additionally, the 5 LSB bits of the E/S register

(E[4:0]) are also loaded with the scratchpad offset address. For each subsequent data byte, both the scratchpad

offset address and the E/S bits (E[4:0]) are incremented. If the data byte is partial, that data byte is ignored and a

error flag called the partial byte flag (PF) is set. This flag is also set if full 2-byte address is not received. This flag

is cleared once the device receives a complete 2-byte address.

During the execution of the Write Scratchpad command, the internal CRC generator computes the 16-bit CRC

based on the data stream which includes the write scratchpad command (0Fh), the 2-byte address and the

data bytes. This CRC is generated using the CRC16 polynomial (X16 + X15 + X2 + 1) by first clearing the CRC

generator. The Write Scratchpad command sequence can be terminated by the host at any time by issuing a

RESET command. The host can read the 16-bit CRC generated by the TMF0008 when the scratchpad offset

address reaches 11111b.

The TMF0008 memory address range is 0000h to 03D3h, therefore if the host attempts to write beyond the

address range, the internal circuitry of the device sets the six most significant address bits to zero as the 2-byte

address is shifted into the internal address register. This modified address can be read back from the Read

Scratchpad command. If the host issues a Copy Scratchpad command without reading the scratchpad and

verifying the address and the data bytes, the memory contents in the scratchpad is not copied to the destination

FRAM memory. If the host attempts to write to a memory location that is write-protected, the device copies the

data byte from the 2-byte address from the FRAM memory into the scratchpad instead of the data byte written

by the host. In a similar manner, if the host attempts to write to a memory location that is EEPROM-protected,

the device copies the bit-wise logical AND of the data byte written by the host and the data byte from the 2-byte

address from the FRAM memory into the scratchpad.

6.5.4.2 Read Scratchpad Command [AAh]

To read the scratchpad, the host issues the Read Scratchpad command (AAh) and then reads the 2-byte

address, the Ending Offset/Data Status byte (E/S) and finally the scratchpad data starting at the scratchpad

offset address. The host verifies the address, E/S byte, and the scratchpad data match with the information

transmitted during the Write Scratchpad command. The validity of the 2-byte address and the scratchpad data

can be verified with the Read Scratchpad command. The host can read the inverted CRC16 once the end of the

scratchpad is reached. If the host continues to read after reading the 2 CRC bytes, the host only receives 1s.

6.5.4.3 Copy Scratchpad [55h]

To copy the data from the scratchpad to the FRAM memory, the host can issue the Copy Scratchpad command

(55h), followed by the 2-byte address and the E/S byte (referred to as Authorization code) obtained from the

Read Scratchpad command. The device copies the scratchpad to the FRAM memory beginning with the target

address and ending with the target address plus the scratchpad offset address listed in the E/S byte only if

the authorization code matches with the E/S byte, the PF flag is not set and the target address is within in

the addressable range. If the host continues to read, the device transmits alternating 0s and 1s. The host can

terminate the Copy Scratchpad command sequence by issuing a reset pulse but only after tPROG duration has

elapsed. The TMF0008 does not allow the memory copy by resetting the AA flag if the memory pages are

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SLVSIV3 – JULY 2025

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