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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： | 4/13页 |
| 文件大小： | 64K |
| 代理商： | DS1215 |
APPLICATION NOTE 52
022394 4/13
COMMON DIFFICULTIES
Cannot Access Clock Registers
Several items can cause this phenomena.
1. Comparison register pointer has has not been set to
the first bit. The Phantom Real Time Clock hides
behind the SRAM and waits for a match to it’s 64–bit
access pattern. In this mode (the pattern match
mode), every write operation to the RAM will be
interpreted as an attempt to match the access pat-
tern by matching the value written to DQ0 (D for the
DS1215) to the pattern bit pointed to by the pattern
match pointer. It is possible that a partial match of
the pattern can occur during normal operation of a
system. It is best to assume that there is a partial
match of the access pattern and that the comparison
register pointer is not pointing to the first bit of the
match pattern. Therefore, the comparison register
pointer must be reset to the first pattern bit before
writing the match pattern. This is accomplished by
performing one read operation of the RAM before
writing the match pattern.
2. Device is in clock access mode after system reset or
interrupt. It is possible that during the course of pre-
vious operation, the Phantom Clock had been
accessed, but had not gone back into pattern match
mode before a system reset or interrupt occurred.
In other words, data bits would be written to or read
from the Phantom Clock registers rather than the
RAM. A solution to this problem is to execute 65
consecutive read cycles immediately after an inter-
rupt or system reset. This will insure that the device
is taken out of the clock access mode (by reading a
maximum of 64 bits) and will reset the comparison
register pointer.
3. Access pattern has been input in reverse order.
Insure that the pattern is input in the following order.
Start with bit 0 of byte 0 continuing to bit 7 of byte 7.
4. Device is being reset. Insure that the device is not
accidentally being reset. This can especially be a
problem with the DS1216C, DS1216D, and
DS1244Y where the reset pin is shared with an
address pin. In this situation, that particular address
line must never be taken low unless the reset bit
(byte 4, bit 4) of the Phantom Clock is disabled,
otherwise the device will be reset and the data trans-
fer will be aborted.
5. Device is in constant write protect mode. If only one
battery is being used for the DS1215, ensure that the
BAT2 pin is grounded. If this pin remains floating it
is possible that the device will think that a power fail
condition has occurred. This is due to the method in
which power fail is detected. A power fail is deter-
mined to have occurred when V
CC
is less than V
TP
,
which is equal to 1.26 x V
BAT
. If V
BAT2
is floating, it
is possible that the node could float to a value such
that V
TP
is equal to V
CC
and thus the device will
always be in a write protect mode.
Device Will Not Oscillate
1. Oscillator enable bit is disabled. Insure that the
oscillator enable bit (bit 5 of byte 4) is at logic 0.
2. Wrong crystal used (DS1215). Insure that the cor-
rect crystal is being used. It is very important that a
crystal with a load capacitance of 6 pF is used. Dal-
las Semiconductor recommends Seiko part number
DS–VT–200, Daiwa part number DT–26S, or equiv-
alent.
3. Poor crystal connection (DS1215). To insure the
greatest performance, insure that the crystal is
placed as close as possible to the crystal input pins.
It should also be mentioned that the DS1215 does
not require load capacitors or feedback resistors.
Note: It should also be mentioned that it is difficult to
determine if the device is oscillating by trying to mea-
sure the frequency with an oscilloscope probe. This is
because of the loading caused by the scope probe
which can kill the oscillator.
Timekeeping Inaccurate
1. Input pins driven higher than V
CC
. It is very impor-
tant to insure that input pins never go above V
CC
. If
any input is allowed to go above V
CC
, it is possible
that the oscillator may be briefly stopped which will
cause the device to lose time.
2. Wrong crystal used (DS1215). For best accuracy,
insure that the correct crystal is used.
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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