DS2438AZ/T&R Maxim Integrated Products, DS2438AZ/T&R Datasheet - Page 20
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DS2438AZ/T&R
Manufacturer Part Number
DS2438AZ/T&R
Description
IC MONITOR SMART BATTERY 8-SOIC
Manufacturer
Maxim Integrated Products
Datasheet
1.DS2438Z.pdf
(29 pages)
Specifications of DS2438AZ/T&R
Function
Fuel, Gas Gauge/Monitor
Battery Type
Smart Batteries
Voltage - Supply
2.4 V ~ 10 V
Operating Temperature
-40°C ~ 85°C
Mounting Type
Surface Mount
Package / Case
8-SOIC (0.154", 3.90mm Width)
Lead Free Status / RoHS Status
Contains lead / RoHS non-compliant
16. The bus master writes a 0 bit. This decouples ROM3, and leaving only ROM2.
17. The bus master reads the remainder of the ROM bits for ROM2 and communicates to the underlying
18. The bus master starts a new ROM search by repeating steps 13 through 15.
19. The bus master writes a 1 bit. This decouples ROM2, leaving only ROM3.
20. The bus master reads the remainder of the ROM bits for ROM3 and communicates to the underlying
Note that the bus master learns the unique ID number (ROM data pattern) of one 1-Wire device on each
ROM Search operation. The time required to derive the part’s unique ROM code is:
The bus master is therefore capable of identifying 75 different 1-Wire devices per second.
MEMORY COMMAND FUNCTIONS
The following command protocols are summarized in Table 11, and by the flowchart of Figure 6.
Write Scratchpad [4Ehxxh]
This command writes to the scratchpad page xxh of the DS2438. The entire 8-byte scratchpad space may
be written, but all writing begins with the byte present at address 0 of the selected scratchpad. After
issuing this command, the user must send the page number of the scratchpad to be written; then the user
may begin writing data to the DS2438 scratchpad. Writing may be terminated at any point by issuing a
reset. Valid page numbers for writing are 00h-07h.
Read Scratchpad [BEhxxh]
This command reads the contents of the scratchpad page xxh on the DS2438. After issuing this command,
the user must send the page number of the scratchpad to be read, and then may begin reading the data,
always beginning at address 0 of the selected scratchpad. The user may read through the end of the
scratchpad space (byte 07h), with any reserved data bits reading all logic 1s, then read the CRC of the
data, and after which the data read will be all logic 1s. If not all locations are to be read, the master may
issue a reset to terminate reading at any time. Valid page numbers are 00h - 07h.
Copy Scratchpad [48hxxh]
This command copies the scratchpad page xxh into the EEPROM / SRAM memory page xxh of the
DS2438. After issuing this command, the user must write a page number to direct which page of memory
the scratchpad is to be copied. Valid page numbers are 00h - 07h. During the copy function, the NVB bit
in the Status/Configuration register will be set to a “l”. When the copy is complete, this bit will reset to
“0”. If the bus master issues read time slots following this command, the DS2438 will output “0” on the
bus as long as it is busy copying the scratchpad to SRAM/EEPROM; it will return a “1” when the copy
process is complete.
logic if desired. This completes the third ROM search pass, in which another of the ROMs was found.
logic if desired. This completes the fourth ROM search pass, in which another of the ROMs was
found.
960 ms + (8 + 3 x 64) 61 ms = 13.16 ms
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