DS2784G+T&R Maxim Integrated Products, DS2784G+T&R Datasheet - Page 36

• Manufacturer Part Number: DS2784G+T&R
• Description: IC FUEL GAUGE STND-ALONE 14-TDFN
• Manufacturer: Maxim Integrated Products

Specifications of DS2784G+T&R

• Function: Fuel, Gas Gauge/Monitor
• Battery Type: Lithium-Ion (Li-Ion), Lithium-Polymer (Li-Pol)
• Voltage - Supply: 2.5 V ~ 4.6 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 14-TDFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

DS2784: 1-Cell Stand-Alone Fuel Gauge IC with Li+ Protector and SHA-1 Authentication
Search Net Address [F0h]. This command allows the bus master to use a process of elimination to identify the
1-Wire net addresses of all slave devices on the bus. The search process involves the repetition of a simple three-
step routine: read a bit, read the complement of the bit, then write the desired value of that bit. The bus master
performs this simple three-step routine on each bit location of the net address. After one complete pass through all
64 bits, the bus master knows the address of one device. The remaining devices can then be identified on
®
additional iterations of the process. See Chapter 5 of the Book of iButton
Standards for a comprehensive
discussion of a net address search, including an actual example (www.maxim-ic.com/iButtonBook).
FUNCTION COMMANDS
After successfully completing one of the net address commands, the bus master can access the features of the
DS2784 with any of the function commands described in the following paragraphs. The name of each function is
followed by the 8-bit op code for that command in square brackets. The function commands are summarized below
in Table 11.
Read Data [69h, XX]. This command reads data from the DS2784 starting at memory address XX. The LSb of the
data in address XX is available to be read immediately after the MSb of the address has been entered. Because
the address is automatically incremented after the MSb of each byte is received, the LSb of the data at address
XX + 1 is available to be read immediately after the MSb of the data at address XX. If the bus master continues to
read beyond address FFh, data is read starting at memory address 00 and the address is automatically
incremented until a reset pulse occurs. Addresses labeled “Reserved” in the memory map contain undefined data
values. The Read Data command can be terminated by the bus master with a reset pulse at any bit boundary.
Reads from EEPROM block addresses return the data in the shadow RAM. A Recall Data command is required to
transfer data from the EEPROM to the shadow. See Table 7 for more details.
Write Data [6Ch, XX]. This command writes data to the DS2784 starting at memory address XX. The LSb of the
data to be stored at address XX can be written immediately after the MSb of address has been entered. Because
the address is automatically incremented after the MSb of each byte is written, the LSb to be stored at address XX
+ 1 can be written immediately after the MSb to be stored at address XX. If the bus master continues to write
beyond address FFh, the data starting at address 00 is overwritten. Writes to read-only addresses, reserved
addresses and locked EEPROM blocks are ignored. Incomplete bytes are not written. Writes to unlocked EEPROM
block addresses modify the shadow RAM. A Copy Data command is required to transfer data from the shadow to
the EEPROM. See Table 7 for more details.
Copy Data [48h, XX]. This command copies the contents of the EEPROM shadow RAM to EEPROM cells for the
EEPROM block containing address XX. Copy Data commands that address locked blocks are ignored. While the
copy data command is executing, the EEC bit in the EEPROM register is set to 1 and writes to EEPROM
addresses are ignored. Reads and writes to non-EEPROM addresses can still occur while the copy is in progress.
The Copy Data command takes t
time to execute, starting on the next falling edge after the address is
EEC
transmitted.
Recall Data [B8h, XX]. This command recalls the contents of the EEPROM cells to the EEPROM shadow memory
for the EEPROM block containing address XX.
Lock [6Ah, XX]. This command locks (write protects) the block of EEPROM containing address XX. The lock bit in
the EEPROM register must be set to 1 before the Lock command is executed. To help prevent unintentional locks,
one must issue the Lock command immediately after setting the lock bit (EEPROM register, address 1Fh, bit 06) to
a 1. If the lock bit is 0 or if setting the lock bit to 1 does not immediately precede the Lock command, the Lock
command has no effect. The Lock command is permanent; a locked block can never be written again.
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