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X1288S16 参数 Datasheet PDF下载

X1288S16图片预览
型号: X1288S16
PDF下载: 下载PDF文件 查看货源
内容描述: 2线RTC实时时钟/日历/ CPU监控器, EEPROM [2-Wire RTC Real Time Clock/Calendar/CPU Supervisor with EEPROM]
分类和应用: 计时器或实时时钟微控制器和处理器外围集成电路光电二极管监控可编程只读存储器电动程控只读存储器电可擦编程只读存储器
文件页数/大小: 31 页 / 559 K
品牌: XICOR [ XICOR INC. ]
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Preliminary Information  
X1288  
When used as frequency output, this signal has a fre-  
quency of 32.768kHz, 100Hz, 1Hz or inactive.  
leap-year correction. The clock also corrects for  
months having fewer than 31 days and has a bit that  
controls 24 hour or AM/PM format. When the X1288  
When used as interrupt output, this signal notifies a  
host processor that an alarm has occurred and an  
action is required. It is an active LOW output.  
powers up after the loss of both V  
and V  
, the  
CC  
BACK  
clock will not operate until at least one byte is written to  
the clock register.  
The control bits for this function are FO1 and FO0 and  
are found in address 0011h of the Clock Control Mem-  
ory map. See “Programmable Frequency Output Bits—  
FO1, FO0” on page 15.  
Reading the Real Time Clock  
The RTC is read by initiating a Read command and  
specifying the address corresponding to the register of  
the Real Time Clock. The RTC Registers can then be  
read in a Sequential Read Mode. Since the clock runs  
continuously and a read takes a finite amount of time,  
there is the possibility that the clock could change during  
the course of a read operation. In this device, the time is  
latched by the read command (falling edge of the clock on  
the ACK bit prior to RTC data output) into a separate latch  
to avoid time changes during the read operation. The  
clock continues to run. Alarms occurring during a read  
are unaffected by the read operation.  
X1, X2  
The X1 and X2 pins are the input and output,  
respectively, of an inverting amplifier. An external  
32.768kHz quartz crystal is used with the X1288 to  
supply a timebase for the real time clock. The  
recommended crystal is a Citizen CFS206-32.768KDZF.  
Internal compensation circuitry is included to form a  
complete oscillator circuit. Care should be taken in the  
placement of the crystal and the layout of the circuit.  
Plenty of ground plane around the device and short  
traces to X1 and X2 are highly recommended. See  
Application section for more information.  
Writing to the Real Time Clock  
The time and date may be set by writing to the RTC  
registers. To avoid changing the current time by an  
uncompleted write operation, the current time value is  
loaded into a separate buffer at the falling edge of the  
clock on the ACK bit before the RTC data input bytes,  
the clock continues to run. The new serial input data  
replaces the values in the buffer. This new RTC value  
is loaded back into the RTC Register by a stop bit at  
the end of a valid write sequence. An invalid write  
operation aborts the time update procedure and the  
contents of the buffer are discarded. After a valid write  
operation the RTC will reflect the newly loaded data  
beginning with the SSEC register reset to “0” at the  
next sub-second update after the stop bit is written.  
The 1Hz frequency output from the PHZ/IRQ pin will  
be reset to restart after the stop bit is written. The RTC  
continues to update the time while an RTC register  
write is in progress and the RTC continues to run dur-  
ing any nonvolatile write sequences. A single byte may  
be written to the RTC without affecting the other bytes.  
Figure 2. Recommended Crystal connection  
X1  
X2  
POWER CONTROL OPERATION  
The power control circuit accepts a V  
and a V  
BACK  
CC  
input. The power control circuit powers the clock from  
when V < V - 0.2V. It will switch back to  
V
BACK  
CC  
BACK  
power the device from V when V exceeds V  
.
CC  
CC  
BACK  
Figure ±. Power Control  
V
CC  
Voltage  
On  
V
BACK  
In  
Off  
Accuracy of the Real Time Clock  
The accuracy of the Real Time Clock depends on the  
frequency of the quartz crystal that is used as the time  
base for the RTC. Since the resonant frequency of a  
crystal is temperature dependent, the RTC performance  
will also be dependent upon temperature. The frequency  
deviation of the crystal is a function of the turnover  
temperature of the crystal from the crystal’s nominal  
REAL TIME CLOCK OPERATION  
The Real Time Clock (RTC) uses an external  
32.768kHz quartz crystal to maintain an accurate inter-  
nal representation of the 1/100 of a second, second,  
minute, hour, day, date, month, and year. The RTC has  
11 of 31  
REV 1.1.30 3/24/04  
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