DS24B33 Maxim, DS24B33 Datasheet - Page 6

• Manufacturer Part Number: DS24B33
• Description: The DS24B33 is a 4096-bit, 1-Wire® EEPROM organized as 16 memory pages of 256 bits each
• Manufacturer: Maxim

1-Wire 4Kb EEPROM
registration number, 32-byte scratchpad, sixteen
32-byte pages of EEPROM, and a CRC-16 generator.
Figure 2 shows the hierarchical structure of the
1-Wire protocol. The bus master must first provide
one of the seven ROM (network) function commands:
Read ROM, Match ROM, Search ROM, Skip ROM,
Resume, Overdrive-Skip ROM, or Overdrive-Match
ROM. Upon completion of an overdrive ROM com-
mand byte executed at standard speed, the device
enters overdrive mode where all subsequent commu-
n i c a t i o n o c c u r s a t a h i g h e r s p e e d . F i g u r e 9
describes the protocol required for these ROM func-
tion commands. After a ROM function command is
s u c c e s s f u l l y e x e c u t e d , t h e m e m o r y f u n c t i o n s
become accessible and the master can provide any
one of the four memory function commands. Figure 7
describes the protocol for these commands. All data
is read and written least significant bit (LSB) first.
Figure 2. Hierarchical Structure for 1-Wire Protocol
Figure 3. 64-Bit Registration Number
iButton is a registered trademark of Maxim Integrated Products, Inc.
6
_______________________________________________________________________________________
MSB
MSB
CRC CODE
8-BIT
MEMORY FUNCTION COMMANDS
FUNCTION COMMANDS
COMMAND LEVEL:
LSB
DS24B33-SPECIFIC
1-Wire ROM
MSB
AVAILABLE COMMANDS:
READ ROM
MATCH ROM
SEARCH ROM
SKIP ROM
RESUME
OVERDRIVE-SKIP ROM
OVERDRIVE-MATCH ROM
WRITE SCRATCHPAD
READ SCRATCHPAD
COPY SCRATCHPAD
READ MEMORY
48-BIT SERIAL NUMBER
Figure 1 shows the parasite power supply. This circuitry
“steals” power whenever the IO input is high. IO pro-
vides sufficient power as long as the specified timing
and voltage requirements are met.
Each DS24B33 contains a unique registration number
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 cyclic redundancy check (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 register and XOR gates as shown in Figure 4. The
polynomial is X
about the 1-Wire CRC is available in Application Note
27: Understanding and Using Cyclic Redundancy
Checks with Maxim iButton
DS24B33
DATA FIELD AFFECTED:
64-BIT REG. #, RC-FLAG
64-BIT REG. #, RC-FLAG
64-BIT REG. #, RC-FLAG
RC-FLAG
RC-FLAG
RC-FLAG, OD-FLAG
64-BIT REG. #, RC-FLAG, OD-FLAG
32-BYTE SCRATCHPAD, FLAGS
32-BYTE SCRATCHPAD
DATA MEMORY
DATA MEMORY
8
+ X
64-Bit Registration Number
5
+ X
LSB
4
®
MSB
+ 1. Additional information
Products .
8-BIT FAMILY CODE
(23h)
Parasite Power
LSB
LSB