TMF0020

COMMAND LEVELS

ROM

COMMANDS

MEMORY

COMMANDS

READ ROM

MATCH ROM

SEARCH ROM

SKIP ROM

RESUME

OVERDRIVE SKIP ROM

OVERDRIVE MATCH ROM

COMMANDS

WRITE SCRATCHPAD

READ SCRATCHPAD

COPY SCRATCHPAD

READ MEMORY

EXTENDED READ MEMORY

Figure 6-7. Command Structure for the TMF0020

6.5.2 Initialization

The host always begins the transaction with the TMF0020 (target) devices through an initialization process. The

initialization process consists of the RESET and PRESENCE pulses. The host generates the RESET pulse,

while the TMF0020 devices acknowledge the RESET pulse with the PRESENCE pulse. The host resets the

TMF0020 devices by driving the SDQ single-wire serial interface bus low for at least 480μs. The PRESENCE

pulse lets the host know that there are one or more TMF0020 devices on the SDQ single-wire serial interface

bus.

6.5.3 ROM Commands

After the host detects the presence of one or more target devices on the SDQ single-wire serial interface bus,

the host can send one of the 8-bit ROM function commands that the TMF0020 supports depending on the use

case scenario. This section describes the scenarios where each of the ROM command can be issued. See

Figure 6-7 for the list of these commands.

6.5.3.1 READ ROM Command [33h]

The READ ROM command sequence (shown in Figure 6-8) starts with the host generating the RESET pulse of

at least 480μs. The device responds with a PRESENCE pulse. Next, the host continues by issuing the READ

ROM command, 33h, and then reads back the 8-bit Family code, 48-bit serial number followed by the 8-bit CRC

using the READ signaling (see the Section 6.5.5.2 section) during the data frame. The READ ROM command

can be issued by the host only if there is a single TMF0020 device on the SDQ single-wire serial interface bus. If

the host issues the command when there are more than 1 target device on the SDQ single-wire serial interface

bus, then a data collision occurs since all the target devices try to respond to the host. The host can identify the

data collision by comparing the CRC from the READ ROM sequence with the computed CRC, which results in a

mismatch.

0

1

1

0

0

0

1

1

CRC (1 BYTE)

Reset

and

Presence

Signals

Read ROM (33h)

Family Code and Identification

Number (7 BYTES)

Figure 6-8. READ ROM Sequence

6.5.3.2 MATCH ROM Command [55h]

When there are multiple targets on the bus, the Match ROM command, 55h, is used by the host to select a

specific target device when the family code and identification number is known. The host issues the Match ROM

command followed by the family code, serial number, and the CRC byte. The target device that matches the

64-bit serial ID is selected and available to perform subsequent memory function commands. The MATCH ROM

command can also be used with a single TMF0020 on the bus.

www.ti.com

TMF0020

SLVSJQ4 – MAY 2026

Copyright © 2026 Texas Instruments Incorporated

Submit Document Feedback

13

Product Folder Links: TMF0020