DS1923 Datasheet, PDF (10/52 Pages) Dallas Semiconductor – Hygrochron Temperature/Humidity Logger iButton with 8kB Data Log Memory

DS1923: Hygrochron Temperature/Humidity Logger iButton with 8kB Data Log Memory
COMMON iButton FEATURES
§ Digital Identification and Information by Momentary Contact
§ Unique Factory-Lasered 64-Bit Registration Number Assures Error-Free Device Selection and Absolute
Traceability Because No Two Parts are Alike
§ Built-in Multidrop Controller for 1-Wire Net
§ Chip-Based Data Carrier Compactly Stores Information
§ Data can be Accessed While Affixed to Object
§ Button Shape is Self-Aligning with Cup-Shaped Probes
§ Durable Stainless-Steel Case Engraved with Registration Number Withstands Harsh Environments
§ Easily Affixed with Self-Stick Adhesive Backing, Latched by its Flange, or Locked with a Ring Pressed onto its
Rim
§ Presence Detector Acknowledges when Reader First Applies Voltage
§ Meets UL#913 (4th Edit.); Intrinsically Safe Apparatus: Approved Under Entity Concept for use in Class I,
Division 1, Group A, B, C, and D Locations (Application Pending)
EXAMPLES OF ACCESSORIES
DS9096P
Self-Stick Adhesive Pad
DS9101
Multipurpose Clip
DS9093RA
Mounting Lock Ring
DS9093A
Snap-In Fob
DS9092
iButton Probe
APPLICATION
The DS1923 is an ideal device to monitor for extended periods of time the temperature and humidity of any object
it is attached to or shipped with, such as fresh produce, medical drugs and supplies and for use in refrigerators and
freezers, as well as for logging climatic data during the transport of sensitive objects and critical processes such as
curing. A 1.27mm diameter hole in the lid of the device allows for air to reach the humidity sensor. The rest of the
electronics inside the DS1923 is sealed so that it is not exposed to ambient humidity. Software for setup and data
retrieval through the 1-Wire interface is available for free download from the iButton website (www.ibutton.com).
This software also includes drivers for the serial and USB port of a PC, and routines to access the general-purpose
memory for storing application- or equipment-specific data files.
OVERVIEW
The block diagram in Figure 1 shows the relationships between the major control and memory sections of the
DS1923. 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 but never read.
The hierarchical structure of the 1-Wire protocol is shown in Figure 2. 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 enters Overdrive mode, where all subsequent
communication occurs at a higher speed. The protocol required for these ROM function commands is described in
Figure 11. After a ROM function command is successfully executed, the memory and control functions become
accessible and the master can provide any one of the eight available commands. The protocol for these memory
and control function commands is described in Figure 9. All data is read and written least significant bit first.
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