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参数资料
| 型号： | DS12887 |
| 厂商： | DALLAS SEMICONDUCTOR |
| 元件分类： | Timer or RTC |
| 英文描述： | 1 TIMER(S), REAL TIME CLOCK, PDIP24 |
| 封装： | DIP-24 |
| 文件页数： | 17/19页 |
| 文件大小： | 584K |
| 代理商： | DS12887 |
DS12887
7 of 19
NONVOLATILE RAM
The 114 general purpose nonvolatile RAM bytes are not dedicated to any special function within the
DS12887. They can be used by the processor program as nonvolatile memory and are fully available
during the update cycle.
INTERRUPTS
The RTC plus RAM includes three separate, fully automatic sources of interrupt for a processor. The
alarm interrupt can be programmed to occur at rates from once per second to once per day. The periodic
interrupt can be selected for rates from 500 ms to 122
s. The update–ended interrupt can be used to
indicate to the program that an update cycle is complete. Each of these independent interrupt conditions is
described in greater detail in other sections of this text.
The processor program can select which interrupts, if any, are going to be used. Three bits in Register B
enable the interrupts. Writing a logic 1 to an interrupt-enable bit permits that interrupt to be initiated when
the event occurs. A 0 in an interrupt-enable bit prohibits the IRQ pin from being asserted from that
interrupt condition. If an interrupt flag is already set when an interrupt is enabled, IRQ is immediately set
at an active level, although the interrupt initiating the event may have occurred much earlier. As a result,
there are cases where the program should clear such earlier initiated interrupts before first enabling new
interrupts.
When an interrupt event occurs, the relating flag bit is set to logic 1 in Register C. These flag bits are set
independently of the state of the corresponding enable bit in Register B. The flag bit can be used in a
polling mode without enabling the corresponding enable bits. The interrupt flag bit is a status bit which
software can interrogate as necessary. When a flag is set, an indication is given to software that an
interrupt event has occurred since the flag bit was last read; however, care should be taken when using the
flag bits as they are cleared each time Register C is read. Double latching is included with Register C so
that bits which are set remain stable throughout the read cycle. All bits which are set (high) are cleared
when read and new interrupts which are pending during the read cycle are held until after the cycle is
completed. One, 2, or 3 bits can be set when reading Register C. Each utilized flag bit should be
examined when read to ensure that no interrupts are lost.
The second flag bit usage method is with fully enabled interrupts. When an interrupt flag bit is set and the
corresponding interrupt enable bit is also set, the IRQ pin is asserted low. IRQ is asserted as long as at
least one of the three interrupt sources has its flag and enable bits both set. The IRQF bit in Register C is
a 1 whenever the IRQ pin is being driven low. Determination that the RTC initiated an interrupt is
accomplished by reading Register C. A logic 1 in bit 7 (IRQF bit) indicates that one or more interrupts
have been initiated by the DS12887. The act of reading Register C clears all active flag bits and the IRQF
bit.
OSCILLATOR CONTROL BITS
When the DS12887 is shipped from the factory, the internal oscillator is turned off. This feature prevents
the lithium energy cell from being used until it is installed in a system. A pattern of 010 in bits 4 through
6 of Register A will turn the oscillator on and enable the countdown chain. A pattern of 11X will turn the
oscillator on, but holds the countdown chain of the oscillator in reset. All other combinations of bits 4
through 6 keep the oscillator off.
相关PDF资料 |
PDF描述 |
|---|---|
| DS1302S | 0 TIMER(S), REAL TIME CLOCK, PDSO8 |
| DS1302N | 0 TIMER(S), REAL TIME CLOCK, PDIP8 |
| DS1302SN | 0 TIMER(S), REAL TIME CLOCK, PDSO8 |
| DS1302 | 0 TIMER(S), REAL TIME CLOCK, PDIP8 |
| DS1302Z | 0 TIMER(S), REAL TIME CLOCK, PDSO8 |
相关代理商/技术参数 |
参数描述 |
|---|---|
| DS12887+ | 功能描述:实时时钟 RTC RoHS:否 制造商:Microchip Technology 功能:Clock, Calendar. Alarm RTC 总线接口:I2C 日期格式:DW:DM:M:Y 时间格式:HH:MM:SS RTC 存储容量:64 B 电源电压-最大:5.5 V 电源电压-最小:1.8 V 最大工作温度:+ 85 C 最小工作温度: 安装风格:Through Hole 封装 / 箱体:PDIP-8 封装:Tube |
| DS12887A | 功能描述:实时时钟 RoHS:否 制造商:Microchip Technology 功能:Clock, Calendar. Alarm RTC 总线接口:I2C 日期格式:DW:DM:M:Y 时间格式:HH:MM:SS RTC 存储容量:64 B 电源电压-最大:5.5 V 电源电压-最小:1.8 V 最大工作温度:+ 85 C 最小工作温度: 安装风格:Through Hole 封装 / 箱体:PDIP-8 封装:Tube |
| DS12887A+ | 功能描述:实时时钟 RTC RoHS:否 制造商:Microchip Technology 功能:Clock, Calendar. Alarm RTC 总线接口:I2C 日期格式:DW:DM:M:Y 时间格式:HH:MM:SS RTC 存储容量:64 B 电源电压-最大:5.5 V 电源电压-最小:1.8 V 最大工作温度:+ 85 C 最小工作温度: 安装风格:Through Hole 封装 / 箱体:PDIP-8 封装:Tube |
| DS1290 | 功能描述:计数器移位寄存器 RoHS:否 制造商:Texas Instruments 计数器类型: 计数顺序:Serial to Serial/Parallel 电路数量:1 封装 / 箱体:SOIC-20 Wide 逻辑系列: 逻辑类型: 输入线路数量:1 输出类型:Open Drain 传播延迟时间:650 ns 最大工作温度:+ 125 C 最小工作温度:- 40 C 封装:Reel |
| DS12C887 | 功能描述:实时时钟 RoHS:否 制造商:Microchip Technology 功能:Clock, Calendar. Alarm RTC 总线接口:I2C 日期格式:DW:DM:M:Y 时间格式:HH:MM:SS RTC 存储容量:64 B 电源电压-最大:5.5 V 电源电压-最小:1.8 V 最大工作温度:+ 85 C 最小工作温度: 安装风格:Through Hole 封装 / 箱体:PDIP-8 封装:Tube |
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