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Maxim Integrated DS1921H Manual

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SPECIAL FEATURES
 Digital thermometer measures temperature in
1/8°C increments with ±1°C accuracy
 Built-in real-time clock (RTC) and timer has
accuracy of ±2 minutes per month from 0°C
to +45°C
 Water resistant or waterproof if placed inside
DS9107 iButton® capsule (Exceeds Water
Resistant 3 ATM requirements)
 Automatically wakes up and measures
temperature at user-programmable intervals
from 1 to 255 minutes
 Logs consecutive temperature measurements
in 2KB of datalog memory
 Records a long-term temperature histogram
with 1/2°C resolution
 Programmable temperature-high and
temperature-low alarm trip points
 Records up to 24 time stamps and durations
when temperature leaves the range specified
by the trip points
 512 bytes of general-purpose battery-backed
SRAM
 Communicates to host with a single digital
signal at 15.4kbits or 125kbits per second
using 1-Wire® protocol
 Fixed range: H: +15°C to +46°C;
Z: -5°C to +26°C
COMMON iButton DEVICE
FEATURES
 Digital identification and information by
momentary contact
 Unique, factory-lasered and tested 64-bit
registration number (8-bit family code + 48-
bit serial number + 8-bit CRC tester) assures
absolute traceability because no two parts are
alike
 Multidrop controller for 1-Wire net
 Chip-based data carrier compactly stores
information
 Data can be accessed while affixed to object
Thermochron, iButton, and 1-Wire are registered trademarks of Maxim Integrated Products, Inc.
DS1921H/DS1921Z
High-Resolution Thermochron
 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
PIN CONFIGURATION
5.89
0.51
IO
GND
All dimensions are shown in millimeters.
ORDERING INFORMATION
PART
DS1921H-F5#
DS1921Z-F5#
#Denotes a RoHS-compliant device that may include lead(Pb) that is
exempt under the RoHS requirements.
EXAMPLES OF ACCESSORIES
DS9096P
DS9101
DS9093RA
DS9093A
DS9092
1 of 45
iButton Devices
16.25
D6
21
3B2000FBC52B
1-Wire
Thermochron
®
TEMP RANGE
PIN-PACKAGE
F5 Can
+15°C to +46°C
F5 Can
-5°C to +26°C
Self-Stick Adhesive Pad
Multi-Purpose Clip
Mounting Lock Ring
Snap-In Fob
iButton Device Probe
19-4887; Rev 11/13
17.35

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Summary of Contents for Maxim Integrated DS1921H

  • Page 1  Multidrop controller for 1-Wire net DS9092 iButton Device Probe  Chip-based data carrier compactly stores information  Data can be accessed while affixed to object Thermochron, iButton, and 1-Wire are registered trademarks of Maxim Integrated Products, Inc. 1 of 45 19-4887; Rev 11/13...
  • Page 2 The DS1921H has a fixed range of +15°C to +46°C. The DS1921Z has a fixed range of -5°C to +26°C. The high resolution makes the DS1921H and DS1921Z suitable for scientific research and development. The general-purpose battery-backed SRAM can store information such as shipping manifests, dates of manufacture, or other relevant data written as ASCII or encrypted files.
  • Page 3 The next 36 bits are a unique serial number. The next 12 bits, called temperature range code, allow distinguishing the DS1921H and DS1921Z from each other and from other DS1921 versions. The last eight bits are a 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.
  • Page 4 DS1921H/Z HIERARCHICAL STRUCTURE FOR 1-Wire PROTOCOL Figure 2 1-Wire net Other Devices Master DS1921 Command Available Cmd. Data Field Level: Commands: Codes: Affected: Read ROM 64-bit Reg. # Match ROM 64-bit Reg. # Search ROM 64-bit Reg. # 1-Wire ROM Function...
  • Page 5 INPUT DATA MEMORY The memory map of the DS1921H/Z is shown in Figure 5. The 4096-bit general-purpose SRAM make up pages 0 through 15. The timekeeping, control, and counter registers fill page 16, called Register Page (see Figure 6). Pages 17 to 19 are assigned to storing the alarm time stamps and durations. The temperature histogram bins begin at page 64 and use up to four pages.
  • Page 6 DS1921H/Z DS1921H/Z REGISTER PAGE MAP Figure 6 ADDR Function Access* 0200h 10 Seconds Single Seconds 0201h 10 Minutes Single Minutes Real- Time 0202h 12/24 20h. 10h. Single Hours R/W; R/W** Clock AM/PM 0203h Day of Week Registers 0204h 10 Date...
  • Page 7 (20 to 23 hours). To distinguish between the days of the week the DS1921H/Z includes a counter with a range from 1 to 7. The assignment of counter value to the day of week is arbitrary. Typically, the number 1 is assigned to a Sunday (U.S.

  • Page 8: Temperature Conversion

    T[7…0] = 8 * ϑ (°C) + 44 (DS1921Z) A value of 23°C, for example, thus translates into 68 decimal or 44h for the DS1921H, and 228 decimal or E4h for the DS1921Z. This corresponds to the binary patterns 0100 0100 and 1110 0100 respectively, which could be written to a Temperature Alarm Register (address 020Bh and 020Ch, respectively).

  • Page 9: Sample Rate

    Sample Rate CONTROL REGISTER The DS1921H/Z is set up for its operation by writing appropriate data to its special function registers that are located in the register page. Several functions that are controlled by a single bit only are combined into a single byte called Control Register (address 20Eh).
  • Page 10 12 hours, and 15 minutes. For a typical mission, the Mission Start Delay is 0. If a mission is too long for a single DS1921H/Z to store all temperature readings at the selected sample rate, one can use several devices, staggering the Mission Start Delay to record the full period.
  • Page 11 DEFINITION MIP: Mission in Progress If this bit reads 1 the DS1921H/Z has been set up for a mission and this mission is still in progress. A mission is started if the EM bit of the Control Register (address 20Eh) is 0 and a non-zero value is written to the Sample Rate Register, address 20Dh.
  • Page 12 There are two alternatives to the way the DS1921H/Z will behave after the 2048 bytes of datalog memory is filled with data. With rollover disabled (RO = 0), the device will fill the datalog memory with the first 2048 mission samples.
  • Page 13 The DS1921H/Z can log high and low durations. The tolerance band is specified by means of the Temperature Alarm Threshold Registers, addresses 20Bh and 20Ch in the register page.
  • Page 14 This procedure is called missioning. First of all, DS1921H/Z needs to have its RTC set to valid time and date. This reference time may be UTC (also called GMT, Greenwich Mean Time) or any other time standard that was chosen for the application.
  • Page 15 The sample rate may be any value from 1 to 255, coded as an unsigned 8-bit binary number. As soon as the sample rate is written, the DS1921H/Z will set the MIP flag and clear the MEMCLR flag. After as many minutes as specified by the Mission Start Delay are over, the device will wait for the next minute boundary, then wake up, copy the current time and date to the Mission Time Stamp Register, and make the first temperature conversion of the mission.
  • Page 16 (Read Only) WRITING WITH VERIFICATION To write data to the DS1921H/Z, the scratchpad has to be used as intermediate storage. First, the master issues the Write Scratchpad command to specify the desired target address, followed by the data to be written to the scratchpad.
  • Page 17 The ending offset/data status byte is unaffected. The hardware of the DS1921H/Z provides a means to accomplish error-free writing to the memory sec- tion. To safeguard data in the 1-Wire environment when reading and to simultaneously speed up data transfers, it is recommended to packetize data into data packets of the size of one memory page each.
  • Page 18 DS1921H/Z MEMORY/CONTROL FUNCTION FLOW CHART Figure 10-1 From ROM Functions Master TX Memory or Flow Chart (Figure 12) Control Fkt. Command To Figure 10 Part Write Read Scratchpad Scratchpad DS1921 sets DS1921 sets EMCLR = 0 EMCLR = 0 Master RX...
  • Page 19 DS1921H/Z MEMORY/CONTROL FUNCTION FLOW CHART Figure 10-2 From Figure 10 To Figure 10 Part Part Copy Read Scratchpad Memory DS1921 sets DS1921 sets EMCLR = 0 EMCLR = 0 Master TX Master TX TA1 (T7:T0), TA2 (T15:T8) TA1 (T7:T0), TA2 (T15:T8)
  • Page 20 DS1921H/Z MEMORY/CONTROL FUNCTION FLOW CHART Figure 10-3 From Figure 10 To Figure 10 Part Part Read Mem. w/CRC DS1921 sets EMCLR = 0 Master TX TA1 (T7:T0), TA2 (T15:T8) Decision made by DS1921 DS1921 sets Memory Address = (T15:T0) End of...
  • Page 21 DS1921H/Z MEMORY/CONTROL FUNCTION FLOW CHART Figure 10-4 From Figure 10 Part Clear Convert Memory Temp. DS1921 sets EMCLR = 0 EMCLR = 1? DS1921 clears Mission Time Stamp, Mission Temperature Con- Samples Counter, Mission in version Process Mission Start Delay,...
  • Page 22 The command works essentially the same way as the simple Read Memory, except for the 16-bit CRC that the DS1921H/Z generates and transmits following the last data byte of a memory page.
  • Page 23 Mission Start and Logging Process The DS1921H/Z does not use a special command to start a mission. Instead, a mission is started by writing a non-zero value to the Sample Rate Register using the Copy Scratchpad command. As shown in Figure 11, a new mission can only be started if the previous mission has been stopped (MIP = 0), the memory is cleared (MEMCLR = 1) and the mission is enabled (EM = 0).

  • Page 24: Hardware Configuration

    16µs (Overdrive speed) or more than 120µs (standard speed), one or more devices on the bus may be reset. Note that the DS1921H/Z does not quite meet the full 16µs maximum low time of the normal 1-Wire bus Overdrive timing. With the DS1921H/Z the bus must be left low for no longer than 15µs at Overdrive speed to ensure that no DS1921H/Z on the 1-Wire bus performs a reset.
  • Page 25 DS1921H/Z is on the bus and is ready to operate. For more details, see the 1-Wire Signaling section.
  • Page 26 DS1921H/Z Search ROM [F0h] When a system is initially brought up, the bus master might not know the number of devices on the 1- Wire bus or their registration numbers. By taking advantage of the wired-AND property of the bus, the master can use a process of elimination to identify the registration numbers of all slave devices.
  • Page 27 DS1921H/Z ROM FUNCTIONS FLOW CHART Figure 13-1 Master TX Reset Pulse From Memory Functions Flow Chart (Figure 10) From Figure 13 Part Short Reset Pulse? OD = 0 DS1921 TX Presence Pulse Master TX ROM Function Command To Figure 13...
  • Page 28 DS1921H/Z ROM FUNCTIONS FLOW CHART Figure 13-2 To Figure 13 Part From Figure 13 Part Skip Overdrive Overdrive ROM? Skip ROM? Match? OD = 1 OD = 1 Master TX Bit 0 Bit 0 Match? Master TX Bit 1 Master TX...
  • Page 29 The initialization sequence required to begin any communication with the DS1921H/Z is shown in Figure 14. A Reset Pulse followed by a Presence Pulse indicates the DS1921H/Z is ready to receive data, given the correct ROM and memory function command. If the bus master uses slew-rate control on the falling edge, it must pull down the line for t to compensate for the edge.
  • Page 30 Wire devices. Read/Write Time Slots Data communication with the DS1921H/Z takes place in time slots that carry a single bit each. Write time slots transport data from bus master to slave. Read time-slots transfer data from slave to master. The definitions of the write and read time slots are illustrated in Figure 15.
  • Page 31 DS1921H/Z will start pulling the data line low; its internal timing generator determines when this pull- down ends and the voltage starts rising again. When responding with a 1, the DS1921H/Z will not hold the data line low at all, and the voltage starts rising as soon as t is over.

  • Page 32: Crc Generation

    With the Write Scratchpad command the CRC is generated by first clearing the CRC generator and then shifting in the command code, the target addresses TA1 and TA2 and all the data bytes. The DS1921H/Z will transmit this CRC only if the data bytes written to the scratchpad include scratchpad ending offset 11111b.
  • Page 33 Indefinite loop where the master reads FFh bytes AA loop Indefinite loop where the master reads AAh bytes Interval during Copy Scratchpad where the DS1921H/Z does not respond. Any bits read Busy during this time are logic 1. 00 loop...
  • Page 34 DS1921H/Z Command-Specific 1-Wire Communication Protocol — Color Codes Master to slave Slave to master Write Scratchpad, reaching the end of the Scratchpad Select <data to EOS> CRC16\ FF loop Write Scratchpad, not reaching the end of the Scratchpad Select <data>...
  • Page 35 DS1921H/Z Read Memory with CRC (invalid address) Select <00 to EOP> CRC16\ <32 bytes> CRC16\ The "32 bytes" are all 00h. Loop Clear Memory Select FF loop To verify success, read the Status Register at address 0214h. If MEMCLR is 1, the command was executed successfully.
  • Page 36 Assumption: The previous mission has come to an end. To end an ongoing mission write the MIP bit in the Status Register to 0. The preparation of a DS1921H/Z for a mission including the start of the mission requires up to four steps: Step 1: set the RTC (if it needs to be adjusted)
  • Page 37 Memory command before proceeding to Step 3. This results in the following data to be written to the Status Register: Address: 20Eh Data: With only a single DS1921H/Z connected to the bus master, the communication of step 2 is as follows: MASTER MODE DATA (LSB FIRST) COMMENTS (Reset) Reset pulse (480μs to 960µs)
  • Page 38 * Writing through address locations 20Fh to 211h is faster than accessing the Mission Start Delay Register in a separate cycle. The write attempt has no effect on the contents of these registers. With only a single DS1921H/Z connected to the bus master, the communication of step 3 is as follows: MASTER MODE...
  • Page 39 14 days. This results in the following data to be written to the special function registers: Address: 20Bh 20Ch 20Dh Data: With only a single DS1921H/Z connected to the bus master, the communication of step 4 is as follows: MASTER MODE DATA (LSB FIRST) COMMENTS (Reset) Reset pulse (480μs to 960µs) (Presence)

  • Page 40: Physical Specification

    IO Voltage to GND -0.5V, +6V IO Sink Current 20mA Temperature Range DS1921H, DS1921Z -40°C to +85°C** Storage Temperature Range -40°C to +50°C** * This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operation sections of this specification is not implied.
  • Page 41 DS1921H/Z PARAMETER SYMBOL CONDITIONS MAX UNITS NOTES Presence Detect High Standard Speed µs Time Overdrive Speed Presence Detect Low Standard Speed µs Time Overdrive Speed Presence Detect Standard Speed µs 1, 16 Sample Time Overdrive Speed IO pin, 1-Wire Write...
  • Page 42 (or other primary) methods of testing and determining the handling methods, quality, and fitness of the articles and products are implemented to further mitigate any risk. Standard Values DS1921H/Z Values Parameter Standard Speed Overdrive Speed...
  • Page 43 DS1921H/Z RTC Frequency Deviation vs Temperature Lower Limit Upper Limit -100 -125 -150 -175 -200 Temperature (°C) Minimum Product Lifetime vs Temperature at Different Sample Rates Every Minute Every 3 Min. Every 10 Min. No Samples Osc. Off 11.00 10.00 9.00...

  • Page 44: Package Information

    DS1921H/Z Minimum Product Lifetime vs Sample Rate at Different Temperatures -5°C 15 °C 26°C 37°C 46°C 12.00 11.00 10.00 9.00 8.00 7.00 6.00 5.00 4.00 3.00 2.00 1.00 1000 Minutes between Samples PACKAGE INFORMATION latest package outline information land patterns (footprints), www.maximintegrated.com/packages.
  • Page 45 Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits) shown in the Electrical Characteristics table are guaranteed.

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