DS1977-F5# Maxim Integrated Products, DS1977-F5# Datasheet

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... Latched by its Flange, or Locked with a Ring Pressed onto its Rim  Presence Detector Acknowledges when Reader 16.25 First Applies Voltage 37 ORDERING INFORMATION 17.35 PART DS1977-F5# #Denotes a RoHS-compliant device that may include lead(Pb) that is exempt under the RoHS requirements. EXAMPLES OF ACCESSORIES PART DS9096P DS9101 DS9093RA DS9093A DS9092 19-4890 ...

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... PHYSICAL SPECIFICATION Size Weight DS1977 ABSOLUTE MAXIMUM RATINGS I/O Voltage to GND I/O Sink Current Junction Temperature Storage Temperature Range Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied ...

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... PUP to be detected as logic '0'. HY has been reached before The actual maximum ε respectively the input-high threshold RLMAX F DS1977 Values Standard Speed Overdrive Speed min max min 1) 1) 65µs (undef.) 8µs 480µs 640µs 48µs 15µs 60µs 2.5µs 60µs 240µ ...

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... Due to its small size and rugged enclosure the device can be carried with a keyring to provide critical data in case of an emergency. The DS1977 can also serve as data shuttle to transport fleet management and vending machine data to an access point for upload into a remote server for further processing ...

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... COMMANDS 64-BIT LASERED ROM Each DS1977 contains a unique ROM code that is 64 bits long. The first 8 bits are a 1-Wire family code. The next 48 bits are a unique serial number. The last 8 bits are a CRC of the first 56 bits. See Figure 3 for details. The 1- Wire CRC is generated using a polynomial generator consisting of a Shift and XOR gates as shown in Figure 4 ...

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... X MEMORY The memory map of the DS1977 is shown in Figure 5. The 32KB of general-purpose EEPROM are located in pages 0 through 510. The passwords and the Password Control register take 17 bytes of page 511. The remaining bytes of page 511 are not accessible to the user. The scratchpad is an additional page that acts as a buffer when writing to the EEPROM memory or setting up a password, and when reading from the EEPROM ...

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... Password Control register), the 64-bit data pattern that the 1-Wire master has to transmit with the command flow is compared to the passwords stored in the DS1977 iButton. The DS1977 delivers the requested data only if the password transmitted by the master was correct or if password checking is not enabled. ...

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... VERSION REGISTER The DS1977 includes a read-only Version register, which is not a component of the memory map. Therefore, a special command is used to read this register. The Chip Revision number enables application software to automatically use the appropriate software driver in case of different logical behavior. ...

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... DS1977. Examples on how to use these functions to operate the DS1977 are included at the end of this document, preceding the Electrical Characteristics section. The communication between master and DS1977 takes place either at standard speed (default Overdrive Speed (OD = 1). If not explicitly set into the Overdrive mode the DS1977 assumes regular speed. ...

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... A pattern of alternating 1's and 0's indicates that the verification was successful, i. e., the password supplied by the master matches the one stored in the DS1977. If the passwords do not match, the master will read a constant stream of FFh bytes until it sends a reset pulse. ...

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... Figure 7 AAh N Read Scratchpad Y Master RX TA1 (T7:T0) Master RX TA2 (T15:T8) Master RX Ending Offset with Data Status (E/S) DS1977 sets Scratch- pad Offset = (T5:T0) Master RX Data Byte from Scratchpad Offset Y Master TX Reset? N Scratch- pad Offset = 3Fh Master RX CRC16 of Command, Address Data, E/S Byte, and Data Starting ...

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... Password DS1977 Copies Scratchpad Data or Data from Password Holding Register (if Password Address) to Memory Strong Pull- up Valid? Y DS1977 TX "0" Master TX Reset? N DS1977 TX "1" Master N TX Reset Figure Authorization Code NOTE: The strong pullup must be activated within 40µs after the last bit of the password is transmitted ...

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... Master TX password is transmitted. 64-Bits [Password] Pullup duration: see t To continue reading the next DS1977 sets Memory memory page, the strong Address = (T15:T0) pullup must be activated within 40µs after the last bit Master Activates of the CRC16 is read. ...

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... Part C3h Verify Password Master TX TA1 (T7:T0), TA2 (T15:T8) Address of Password? DS1977 sets Memory Address = (T15:T3 Master TX Password to verify Master Activates Strong Pullup NOTE: The strong pullup must be activated within 40µs after the last bit of the password is transmitted. Pullup duration: see t ...

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... All transactions on the 1-Wire bus begin with an initialization sequence. The initialization sequence consists of a reset pulse transmitted by the bus master followed by presence pulse(s) transmitted by the slave(s). The presence pulse lets the bus master know that the DS1977 is on the bus and is ready to operate. For more details, see the 1- Wire Signaling section. ...

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... This command allows the bus master to read the DS1977’s 8-bit family code, unique 48-bit serial number, and 8-bit CRC. This command can only be used if there is a single DS1977 on the bus. If more than one slave is present on the bus, a data collision will occur when all slaves try to transmit at the same time (open drain will produce a wired- AND result) ...

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... Y DS1977 TX Presence Pulse 55h F0h N Search ROM Command ? DS1977 TX Bit 0 DS1977 TX Bit 0 Master TX Bit Bit 0 Bit 0 Match ? Match ? Y DS1977 TX Bit 1 DS1977 TX Bit 1 Master TX Bit Bit 1 Bit 1 Match ? Match ? Y DS1977 TX Bit 63 DS1977 TX Bit 63 Master TX Bit Bit 63 Bit 63 Match ? Match ? Memory Functions Flow Chart (Figure 7) ...

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... Part From Figure 9 st A5h 1 Part Resume Command ? From Figure Part To Figure Part 3Ch N Overdrive Skip ROM ? Master TX Reset ? N Y Master TX Reset ? 69h N Overdrive Match ROM ? Master TX Bit Bit 0 Match ? Y Master TX Bit 1 N Bit 1 Match ? Y Master TX Bit 63 N Bit 63 Match ? DS1977 ...

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... The Overdrive Match ROM command followed by a 64-bit ROM sequence transmitted at Overdrive Speed allows the bus master to address a specific DS1977 on a multidrop bus and to simultaneously set it in Overdrive mode. Only the DS1977 that exactly matches the 64-bit ROM sequence will respond to the subsequent memory function command ...

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... Overdrive speed to accommodate other 1-Wire devices. READ/WRITE-TIME SLOTS Data communication with the DS1977 takes place in time slots, which carry a single bit each. Write-time slots transport data from bus master to slave. Read-time slots transfer data from slave to master. The definitions of the write and read-time slots are illustrated in Figure 11 ...

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... During the t RL data line low; its internal timing generator determines when this pulldown ends and the voltage starts rising again. When responding with a 1, the DS1977 will not hold the data line low at all, and the voltage starts rising as soon over. ...

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... ROM. The bus master can compute a CRC value from the first 56 bits of the 64-bit ROM and compare it to the value stored within the DS1977 to determine if the ROM data has been received error-free. The equivalent polynomial function of this CRC is: X received in the true (non-inverted) form ...

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... Indefinite Loop Where the Master Reads AA Bytes Data Transfer to/from EEPROM (Data or Passwords Memory); No Activity on the 1-Wire Strong Pullup Bus Permitted During this Time 16 15 Polynomial = STAGE STAGE STAGE STAGE STAGE STAGE STAGE DESCRIPTION STAGE STAGE STAGE STAGE INPUT DATA DS1977 CRC OUTPUT ...

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... Strong Pullup TA <data to EOS> CRC16\ TA <data> RST PD TA-E/S <data to EOS> CRC16\ TA-E/S <PW/dummy> Strong Pullup TA-E/S <PW/dummy> Strong Pullup TA <PW/dummy> Strong Pullup Strong Pullup TA <PW/dummy> Strong Pullup loop FF loop AA loop FF loop <data to EOP> CRC16\ <64 bytes> CRC16\ FF loop Loop FF loop DS1977 ...

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... ROM and the version register. In the second example, passwords are installed. The third example shows how to write a couple of bytes and how to read adjacent memory pages. EXAMPLE 1 Task: Read the ROM and the version register With only a single DS1977 connected to the bus master, the communication is as follows: MASTER MODE TX RX ...

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... With only a single DS1977 connected to the bus master, the communication is as follows: MASTER MODE Step Step Step (—) (Activate Strong Pullup for Step (—) (Activate Strong Pullup for DATA (LSB FIRST) (Reset) (Presence) CCh 0Fh C0h 7Fh <Read Password> <Full-Access Password> ...

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... Issue Copy Scratchpad with Password Command TA1, Target Address = D0h TA2, Target Address = 7FD0h E/S-Byte Transmit 8 Dummy Bytes as Password, Because Passwords are Not Yet Enabled Supply Power for Programming Read to Check for Programming Success; AAh Means Success Reset Pulse Presence Pulse DS1977 ...

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... With only a single DS1977 connected to the bus master, the communication is as follows: MASTER MODE Step Step Step (—) (Activate Strong Pullup for Step (—) (Activate Strong Pullup for Step 5 (—) (Activate Strong Pullup for DATA (LSB FIRST) (Reset) (Presence) CCh 0Fh ...

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... Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time © 2009 Maxim Integrated Products DESCRIPTION . W0L spec in the EC table. W1L Maxim is a registered trademark of Maxim Integrated Products, Inc. DS1977 PAGES CHANGED ...