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参数资料
| 型号： | DS1215 |
| 厂商： | DALLAS SEMICONDUCTOR |
| 元件分类： | XO, clock |
| 英文描述： | Using the Dallas Phantom Real Time Clocks(实时时钟芯片) |
| 中文描述： | 0 TIMER(S), REAL TIME CLOCK, PDIP16 |
| 文件页数： | 2/13页 |
| 文件大小： | 64K |
| 代理商： | DS1215 |
APPLICATION NOTE 52
022394 2/13
Table 1
DS1215
DS1216B
DS1216C
DS1216D
DS1216E
DS1216F
DS1243Y
DS1244Y
DS1248Y
Phantom Time Chip
SmartWatch/RAM 16K/64K
SmartWatch/RAM 64K/256K
SmartWatch/RAM 256K/1M
SmartWatch/ROM 64K/256K
SmartWatch/ROM 64K/256K/1M
64K NV SRAM with Phantom Clock
256K NV SRAM with Phantom Clock
1024K NV SRAM with Phantom Clock
APPLICATION
The Dallas Phantom Real Time Clock family offers two
features that will greatly enhance a system. The first
feature is nonvolatile RAM capability. The second fea-
ture is that the Phantom Clock is transparent to the RAM
and therefore timekeeping capacity can be added to a
system without changing the existing hardware. All that
is required is an existing bytewide memory socket. The
retrofit capability is maximized through the transparent
interfaces supported by the Phantom Time Chip. Also
advantageous to the designer is that an upgrade path is
provided to higher RAM densities with the DS124X
modules or to higher RAM/ROM densities with the
DS1216.
It should be mentioned that there is some software over-
head that is associated with having timekeeping func-
tions that are transparent to RAM as will be discussed in
detail below. If it is determined that a transparent clock
is not necessary, then the DS164X Nonvolatile Time-
keeping RAM family could offer an excellent solution to
your timekeeping and nonvolatile SRAM needs. These
offer nonvolatile SRAM with the Real Time Clock regis-
ters located in the RAM address space. Another pos-
sible solution are the DS1386 or DS1486 RAMified
Watchdog Timekeepers which offer nonvolatile RAM
and Real Time Clock as well as a few extra features
including alarm function and Watchdog timer.
OPERATION
Nonvolatile RAM Operation
One important feature of the Dallas Phantom Real Time
Clocks is that the nonvolatile RAM can be used to store
system configuration data and since the clock is trans-
parent to the RAM, no memory is lost to timekeeping
needs. When the Phantom Clock is not accessed, the
CE signal is passed on to the chip enable of the memory.
Reading and writing to the RAM is identical to that of a
standard RAM chip. Figure 1 illustrates a typical RAM/
Time Chip interface. Note that this is the basic interface
used for the DS1216 SmartWatch/RAM and the
DS124X.
The Phantom Real Time Clock family performs circuit
functions required to make a CMOS RAM nonvolatile.
First, a switch is provided to direct power from the bat-
tery or V
CC
supply depending on which is greater. The
second function provided is power–fail detection.
Power fail detection occurs when V
CCI
falls below V
TP
,
which is equal to 1.26 x V
BAT
. When V
CCI
goes out of
tolerance, a comparator outputs a power–fail signal to
the chip enable logic. The third function accomplishes
write protection by holding the chip enable signal to the
memory (CEO) within 0.2 volts of V
CC
or battery as long
as V
CC
is out of tolerance. During nominal power supply
conditions the memory chip enable signal (CEO) will
track the chip enable signal (CEI) sent to the socket with
a maximum propagation delay of 20 ns.
Finally, an important consideration when using the
DS1216 is to select a RAM that draws no more than a
maximum of 1
μ
A. If the RAM data retention current is
larger than 1
μ
A, the device will not meet the data reten-
tion expectations of more than 10 years at 25
°
C. In the
10 year data retention calculation for the DS1216, it is
assumed that system power will be on 20% of the time.
Perhaps the best way to insure that a data retention of
10 years at 25
°
C is met is to use one of the DS124X
modules with self–contained nonvolatile RAM. The
DS124X modules will insure data retention for 10 years
regardless of how often the system power is on.
ROM Operation
The DS1215 and DS1216(E/F) can also be used in con-
junction with a ROM. A typical ROM/Time Chip inter-
face is illustrated in Figure 2. In this configuration, the
ROM/RAM pin is connected to V
CCO
to select the ROM
mode of operation. Since ROM is a read–only device
that retains data in the absence of power, battery
back–up and write protection is not required. As a
相关PDF资料 |
PDF描述 |
|---|---|
| DS1216B | SmartWatch/RAM 16K/64K(16K/64K位带实时时钟的掉电保护RAM插座) |
| DS1216C | SmartWatch/RAM 16K/65K(16K/65K位带实时时钟的掉电保护RAM插座) |
| DS1216D(中文) | Using the Dallas Phantom Real Time Clocks(256K/1M位带实时时钟的带掉电保护SRAM插座) |
| DS1216D | Using the Dallas Phantom Real Time Clocks(256K/1M位带实时时钟的带掉电保护SRAM插座) |
| DS1216E | SmartWatch/RAM 16K/66K(16K/66K带实时时钟的ROM或掉电保护RAM插座) |
相关代理商/技术参数 |
参数描述 |
|---|---|
| DS1215G | 制造商:未知厂家 制造商全称:未知厂家 功能描述:Peripheral IC |
| DS1215GN | 制造商:未知厂家 制造商全称:未知厂家 功能描述:Peripheral IC |
| DS-1215ZJ | 制造商:Hikvision USA 功能描述:Camera Pole Mount Plate7.64In X 4.61In X 3.94In 制造商:HIKVISION 功能描述:CAMERA POLE MOUNT PLATE 7.64IN X 4.61IN X 3.94IN |
| DS1216 | 制造商:MAXIM 制造商全称:Maxim Integrated Products 功能描述:SmartWatch RAM (DS1216B/C/D/H); SmartWatch ROM (DS1216E/F) |
| DS1216B | 功能描述:存储器控制器 SmartWatch RAM RoHS:否 制造商:Maxim Integrated |
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