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參數(shù)資料
| 型號： | DS1923 |
| 英文描述： | Hygrochron Temperature/Humidity Logger iButton with 8kB Data Log Memory |
| 文件頁數(shù)： | 42/52頁 |
| 文件大?。?/td> | 495K |
| 代理商： | DS1923 |
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DS1923: Hygrochron Temperature/Humidity Logger iButton with 8kB Data Log Memory
42 of 52
Slave-to-Master
A
read-data
time slot begins like a write-one time slot. The voltage on the data line must remain below V
TL
until the
read-low time t
RL
is expired. During the t
RL
window, when responding with a 0, the DS1923 starts pulling the data
line low; its internal timing generator determines when this pulldown ends and the voltage starts rising again. When
responding with a 1, the DS1923 does not hold the data line low at all, and the voltage starts rising as soon as t
RL
is over.
The sum of t
RL
+ (rise rime) on one side and the internal timing generator of the DS1923 on the other side define
the master sampling window (t
MSRMIN
to t
MSRMAX
) in which the master must perform a read from the data line. For
most reliable communication, t
RL
should be as short as permissible and the master should read close to but no later
than t
MSRMAX
. After reading from the data line, the master must wait until t
SLOT
is expired. This guarantees sufficient
recovery time t
REC
for the DS1923 to get ready for the next time slot.
Improved Network Behavior
In a 1-Wire environment line termination is possible only during transients controlled by the bus master (1-Wire
driver). 1-Wire networks, therefore are susceptible to noise of various origins. Depending on the physical size and
topology of the network, reflections from end points and branch points can add up or cancel each other to some
extent. Such reflections are visible as glitches or ringing on the 1-Wire communication line. Noise coupled onto the
1-Wire line from external sources can also result in signal glitching. A glitch during the rising edge of a time slot can
cause a slave device to lose synchronization with the master and, as a consequence, result in a search ROM
command coming to a dead end or cause a device-specific function command to abort. For better performance in
network applications, the DS1923 uses a new 1-Wire front end, which makes it less sensitive to noise and also
reduces the magnitude of noise injected by the slave device itself.
The 1-Wire front end of the DS1923 differs from traditional slave devices in four characteristics.
1) The falling edge of the presence pulse has a controlled slew rate. This provides a better match to the line
impedance than a digitally switched transistor, converting the high-frequency ringing known from traditional
devices into a smoother low-bandwidth transition. The slew-rate control is specified by the parameter t
FPD
,
which has different values for standard and Overdrive speed.
2) There is additional low-pass filtering in the circuit that detects the falling edge at the beginning of a time slot.
This reduces the sensitivity to high-frequency noise. This additional filtering does not apply at Overdrive speed.
3) There is a hysteresis at the low-to-high switching threshold V
TH
. If a negative glitch crosses V
TH
but does not go
below V
TH
- V
HY
, it will not be recognized (Figure 14, Case A). The hysteresis is effective at any 1-Wire speed.
4) There is a time window specified by the rising edge hold-off time t
REH
during which glitches are ignored, even if
they extend below V
TH
- V
HY
threshold (Figure 14, Case B, t
GL
< t
REH
). Deep-voltage droops or glitches that
appear late after crossing the V
TH
threshold and extend beyond the t
REH
window cannot be filtered out and are
taken as beginning of a new time slot (Figure 14, Case C, t
GL
t
REH
).
Only devices that have the parameters t
FPD
, V
HY
, and t
REH
specified in their electrical characteristics use the
improved 1-Wire front end.
Figure 14. NOISE SUPPRESSION SCHEME
V
PUP
V
TH
V
HY
0V
t
REH
t
GL
t
REH
t
GL
Case A
Case C
Case B
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| DS1923-F5 | Hygrochron Temperature/Humidity Logger iButton with 8kB Data Log Memory |
| DS1990 | Serial Number iButton |
| DS1990A | Serial Number iButton |
| DS1990A-F5 | Serial Number iButton |
| DS1994L-F5 | 4kb Plus Time Memory iButton |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| DS1923_1 | 制造商:DALLAS 制造商全稱:Dallas Semiconductor 功能描述:Hygrochron Temperature/Humidity Logger iButton with 8kB Data Log Memory |
| DS1923_11 | 制造商:MAXIM 制造商全稱:Maxim Integrated Products 功能描述:Hygrochron Temperature/Humidity Logger |
| DS1923-F5 | 功能描述:iButton RoHS:否 存儲類型:SRAM 存儲容量:512 B 組織: 工作電源電壓:3 V to 5.25 V 接口類型:1-Wire 最大工作溫度:+ 85 C 尺寸:17.35 mm x 5.89 mm 封裝 / 箱體:F5 MicroCan 制造商:Maxim Integrated |
| DS1923-F5# | 功能描述:iButton Hygrochron Temp/Hum Logger w/8KB DataLog RoHS:否 存儲類型:SRAM 存儲容量:512 B 組織: 工作電源電壓:3 V to 5.25 V 接口類型:1-Wire 最大工作溫度:+ 85 C 尺寸:17.35 mm x 5.89 mm 封裝 / 箱體:F5 MicroCan 制造商:Maxim Integrated |
| DS1923-F5#W | 功能描述:iButton Hygrochron Temp/Hum Logger w/8KB DataLog RoHS:否 存儲類型:SRAM 存儲容量:512 B 組織: 工作電源電壓:3 V to 5.25 V 接口類型:1-Wire 最大工作溫度:+ 85 C 尺寸:17.35 mm x 5.89 mm 封裝 / 箱體:F5 MicroCan 制造商:Maxim Integrated |
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