DS2422 Maxim, DS2422 Datasheet - Page 8

• Manufacturer Part Number: DS2422
• Description: The DS2422 temperature/data logger combines the core functions of a fully featured data logger in a single chip
• Manufacturer: Maxim

Figure 3. DS2422 Block Diagram
OVERVIEW
The block diagram in Figure 3 shows the relationships between the major control and memory sections of the
DS2422. The device has six main data components: 1) 64-bit lasered ROM, 2) 256-bit scratchpad, 3) 512-byte
general-purpose SRAM, 4) two 256-bit register pages of timekeeping, control, status, and counter registers and
passwords, 5) 64 bytes of calibration memory, and 6) 8192 bytes of data-logging memory. Except for the ROM and
the scratchpad, all other memory is arranged in a single linear address space. The data-logging memory, counter
registers and several other registers are read-only for the user. Both register pages are write-protected while the
device is programmed for a mission. The password registers, one for a read password and another one for a
read/write password can only be written to, never read.
The hierarchical structure of the 1-Wire protocol is shown in Figure 4. The bus master must first provide one of the
eight ROM function commands: 1) Read ROM, 2) Match ROM, 3) Search ROM, 4) Conditional Search ROM, 5)
Skip ROM, 6) Overdrive-Skip ROM, 7) Overdrive-Match ROM or 8) Resume. Upon completion of an Overdrive
ROM command byte executed at standard speed, the device will enter Overdrive mode, where all subsequent
communication occurs at a higher speed. The protocol required for these ROM function commands is described in
Figure 14. After a ROM function command is successfully executed, the memory and control functions become
accessible and the master may provide any one of the eight available commands. The protocol for these memory
and control function commands is described in Figure 12. All data is read and written least significant bit first.
PUMP_ONZ
CNVST
SDATA
VPAD
SCLK
1-Wire
Port
Powered by VBAT
3V Lithium
Structures
5V Pad
32.768kHz
Oscillator
Thermal
Sense
I/O
All circuitry is powered by the battery
unless otherwise specified
ADC1
Timekeeping &
Control Reg. &
Function
Control
ROM
Counters
Control
8 of 49
Internal
Logic
Calibration Memory
General-Purpose
Register Pages
(512 Bytes)
Lasered
(64 Bytes)
(64 Bytes)
64-Bit
Memory
ROM
Datalog
SRAM
8KB
Function
Memory
Control
Powered
Parasite
Circuitry
Scratchpad
256-Bit