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DS1921G
Thermochron iButton Device
ory. Except for the ROM and the scratchpad, all other
memory is arranged in a single linear address space.
All memory reserved for logging purposes, including
counter registers and several other registers, is read-
only for the user. The timekeeping and control regis-
ters are write protected while the device is
programmed for a mission.
The hierarchical structure of the 1-Wire protocol is
shown in Figure 2. The bus master must first provide
one of the seven ROM function commands: Read ROM,
Match ROM, Search ROM, Conditional Search ROM,
Skip ROM, 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 communi-
cation occurs at a higher speed. The protocol required
for these ROM function commands is described in
Figure 13. After a ROM function command is success-
fully executed, the memory functions become accessi-
ble and the master can provide any one of the seven
available commands. The protocol for these memory
function commands is described in Figure 10. All data
is read and written least significant bit first.
Parasite Power
Figure 1 shows the parasite-powered circuitry. This cir-
cuitry “steals” power whenever the IO input is high. IO
provides sufficient power as long as the specified tim-
ing and voltage requirements are met. The advantages
of parasite power are two-fold: 1) By parasiting off this
input, battery power is not consumed for 1-Wire ROM
function commands, and 2) if the battery is exhausted
for any reason, the ROM may still be read normally. The
remaining circuitry of the DS1921G is solely operated
by battery energy. As a consequence, if the battery is
exhausted, all memory data is lost including the data of
the last mission, and no new mission can be started.
Refer to Application Note 5057: OneWireViewer Tips
and Tricks for how to check the battery status.
BUS
MASTER
1-Wire NET
OTHER DEVICES
DS1921G
COMMAND LEVEL:
1-Wire ROM
FUNCTION COMMANDS
AVAILABLE COMMANDS:
READ ROM
MATCH ROM
SEARCH ROM
SKIP ROM
OVERDRIVE-SKIP ROM
OVERDRIVE-MATCH ROM
CONDITIONAL SEARCH ROM
COMMAND CODES:
33h
55h
F0h
CCh
3Ch
69h
ECh
DATA FIELD AFFECTED:
64-BIT ROM
64-BIT ROM
64-BIT ROM
N/A
OD-FLAG
64-BIT ROM, OD-FLAG
64-BIT ROM, CONDITIONAL SEARCH
SETTINGS, DEVICE STATUS
WRITE SCRATCHPAD
READ SCRATCHPAD
COPY SCRATCHPAD
0Fh
AAh
55h
256-BIT SCRATCHPAD, FLAGS
256-BIT SCRATCHPAD
4096-BIT SRAM, REGISTERS, FLAGS
DS1921G-SPECIFIC
MEMORY/CONTROL
FUNCTION COMMANDS
READ MEMORY
READ MEMORY WTH CRC
CLEAR MEMORY
F0h
A5h
3Ch
ALL MEMORY
ALL MEMORY
MISSION TIMESTAMP, MISSION SAMPLES COUNTER,
START DELAY, SAMPLE RATE, ALARM TIMESTAMPS
AND DURATIONS, HISTOGRAM MEMORY
CONVERT TEMPERATURE
Figure 2. Hierarchical Structure for 1-Wire Protocol
8
44h
MEMORY ADDRESS 211h
Maxim Integrated
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相关代理商/技术参数
DS1921G-F5#W
功能描述:iButton RoHS:否 存储类型:SRAM 存储容量:512 B 组织: 工作电源电压:3 V to 5.25 V 接口类型:1-Wire 最大工作温度:+ 85 C 尺寸:17.35 mm x 5.89 mm 封装 / 箱体:F5 MicroCan 制造商:Maxim Integrated
DS1921G-F5/A0C
功能描述:iButton
RoHS:否 存储类型:SRAM 存储容量:512 B 组织: 工作电源电压:3 V to 5.25 V 接口类型:1-Wire 最大工作温度:+ 85 C 尺寸:17.35 mm x 5.89 mm 封装 / 箱体:F5 MicroCan 制造商:Maxim Integrated
DS1921G-F5/A12
功能描述:iButton
RoHS:否 存储类型:SRAM 存储容量:512 B 组织: 工作电源电压:3 V to 5.25 V 接口类型:1-Wire 最大工作温度:+ 85 C 尺寸:17.35 mm x 5.89 mm 封装 / 箱体:F5 MicroCan 制造商:Maxim Integrated
DS1921G-F5/A12-W
功能描述:iButton
RoHS:否 存储类型:SRAM 存储容量:512 B 组织: 工作电源电压:3 V to 5.25 V 接口类型:1-Wire 最大工作温度:+ 85 C 尺寸:17.35 mm x 5.89 mm 封装 / 箱体:F5 MicroCan 制造商:Maxim Integrated
DS1921G-F5/A14
功能描述:iButton
RoHS:否 存储类型:SRAM 存储容量:512 B 组织: 工作电源电压:3 V to 5.25 V 接口类型:1-Wire 最大工作温度:+ 85 C 尺寸:17.35 mm x 5.89 mm 封装 / 箱体:F5 MicroCan 制造商:Maxim Integrated
DS1921G-F5/A15
功能描述:iButton
RoHS:否 存储类型:SRAM 存储容量:512 B 组织: 工作电源电压:3 V to 5.25 V 接口类型:1-Wire 最大工作温度:+ 85 C 尺寸:17.35 mm x 5.89 mm 封装 / 箱体:F5 MicroCan 制造商:Maxim Integrated
DS1921G-F5/A17
功能描述:iButton
RoHS:否 存储类型:SRAM 存储容量:512 B 组织: 工作电源电压:3 V to 5.25 V 接口类型:1-Wire 最大工作温度:+ 85 C 尺寸:17.35 mm x 5.89 mm 封装 / 箱体:F5 MicroCan 制造商:Maxim Integrated
DS1921G-F5/A1B
功能描述:iButton
RoHS:否 存储类型:SRAM 存储容量:512 B 组织: 工作电源电压:3 V to 5.25 V 接口类型:1-Wire 最大工作温度:+ 85 C 尺寸:17.35 mm x 5.89 mm 封装 / 箱体:F5 MicroCan 制造商:Maxim Integrated