DS1302实时时钟芯片详解及特性

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"DS1302是一款实时时钟（RTC）芯片，适用于单片机学习者和项目开发。该芯片具有多种功能和优势，包括精确的时间计数、低功耗以及简单的接口设计。它还提供了额外的数据存储空间和与DS1202的兼容性，同时增加了如涓流充电等功能。" DS1302时钟芯片是用于嵌入式系统和电子设备中的实时时钟解决方案。以下是对这款芯片的详细解析： 1. **时间计数功能**：DS1302能够精确地计数秒、分钟、小时、日期、月份、星期以及年份，并且内置闰年补偿机制，有效范围直至2100年。这使得它能够在各种应用中提供准确的定时和日历功能。 2. **31x8 RAM**：除了时钟功能，DS1302还包含31字节的随机存取内存（RAM），可用于存储临时数据或配置信息，这在需要保持数据的系统中非常有用。 3. **串行I/O**：为了减少引脚数量，DS1302采用串行输入/输出接口，通过三条线（SCLK、I/O和RST）即可完成数据传输，这对于资源有限的微控制器平台来说非常理想。 4. **电压范围**：芯片可以在2.0至5.5伏的电压范围内工作，同时在2.0伏时功耗低于300nA，这意味着它能适应各种电源条件，并在低功耗场景下表现良好。 5. **数据传输**：支持单字节和多字节（突发模式）数据传输，允许读写时钟或RAM数据，提高了数据处理效率。 6. **封装形式**：提供8引脚双列直插式封装（DIP）和8引脚小外形集成电路封装（SOIC），适合表面安装，满足不同设计需求。 7. **3-wire接口**：DS1302采用简单的3线接口，包括SCLK（时钟信号）、I/O（数据输入/输出）和RST（复位）引脚，易于实现通信协议。 8. **TTL兼容**：在VCC=5V时，DS1302的接口与TTL电平兼容，方便与常见的微控制器进行连接。 9. **工业温度范围**：可选的工业级温度范围从-40°C到+85°C，确保了在极端环境下的稳定工作。 10. **DS1202兼容性**：DS1302与DS1202时钟芯片兼容，便于现有系统升级或替换。 11. **新增特性**：相比DS1202，DS1302增加了涓流充电能力（VCC1），支持主电源和备用电源双电源引脚，以及作为电池或超级电容输入的备用电源引脚，还增加了7字节的额外擦写垫内存。 12. **引脚定义**：DS1302的引脚包括VCC1和VCC2（电源引脚）、SCLK（时钟输入）、I/O（数据输入/输出）、RST（复位）、X1和X2（32.768kHz晶体振荡器的连接点）以及GND（接地）。总结起来，DS1302是一款功能强大、低功耗、易于集成的时钟芯片，特别适合需要精确时间管理和数据存储的单片机应用。其独特的特性和广泛的兼容性使其成为许多项目开发者的首选时钟解决方案。

DS1302

032598 3/12

RESET AND CLOCK CONTROL

All data transfers are initiated by driving the RST input

high. The RST input serves two functions. First, RST

turns on the control logic which allows access to the shift

the RST

signal provides a method of terminating either

single byte or multiple byte data transfer.

A clock cycle is a sequence of a falling edge followed by

a rising edge. For data inputs, data must be valid during

the rising edge of the clock and data bits are output on

the falling edge of clock. If the RST

input is low all data

transfer terminates and the I/O pin goes to a high imped-

ance state. Data transfer is illustrated in Figure 3. At

power–up, RST

must be a logic “0” until V

2.0 volts.

Also SCLK must be at a logic “0” when RST is driven to a

logic “1” state.

DATA INPUT

Following the eight SCLK cycles that input a write com-

mand byte, a data byte is input on the rising edge of the

next eight SCLK cycles. Additional SCLK cycles are

ignored should they inadvertently occur. Data is input

starting with bit 0.

DATA OUTPUT

Following the eight SCLK cycles that input a read com-

mand byte, a data byte is output on the falling edge of

the next eight SCLK cycles. Note that the first data bit to

be transmitted occurs on the first falling edge after the

last bit of the command byte is written. Additional SCLK

cycles retransmit the data bytes should they inadver-

tently occur so long as RST

remains high. This opera-

tion permits continuous burst mode read capability.

Also, the I/O pin is tri–stated upon each rising edge of

SCLK. Data is output starting with bit 0.

BURST MODE

Burst mode may be specified for either the clock/calen-

dar or the RAM registers by addressing location 31 deci-

mal (address/command bits one through five = logical

one). As before, bit six specifies clock or RAM and bit 0

specifies read or write. There is no data storage capac-

ity at locations 9 through 31 in the Clock/Calendar Reg-

isters or location 31 in the RAM registers. Reads or

writes in burst mode start with bit 0 of address 0.

As in the case with the DS1202, when writing to the

clock registers in the burst mode, the first eight registers

must be written in order for the data to be transferred.

However, when writing to RAM in burst mode it is not

necessary to write all 31 bytes for the data to transfer.

Each byte that is written to will be transferred to RAM

regardless of whether all 31 bytes are written or not.

CLOCK/CALENDAR

The clock/calendar is contained in seven write/read reg-

isters as shown in Figure 4. Data contained in the clock/

calendar registers is in binary coded decimal format

(BCD).

CLOCK HALT FLAG

Bit 7 of the seconds register is defined as the clock halt

flag. When this bit is set to logic “1”, the clock oscillator is

stopped and the DS1302 is placed into a low–power

standby mode with a current drain of less than 100

nanoamps. When this bit is written to logic “0”, the clock

will start. The initial power on state is not defined.

AM-PM/12-24 MODE

Bit 7 of the hours register is defined as the 12– or

24–hour mode select bit. When high, the 12–hour mode

is selected. In the 12–hour mode, bit 5 is the AM/PM bit

with logic high being PM. In the 24–hour mode, bit 5 is

the second 10 hour bit (20 – 23 hours).

WRITE PROTECT BIT

Bit 7 of the control register is the write protect bit. The

first seven bits (bits 0 – 6) are forced to zero and will

always read a zero when read. Before any write opera-

tion to the clock or RAM, bit 7 must be zero. When high,

the write protect bit prevents a write operation to any

other register. The initial power on state is not defined.

Therefore the WP bit should be cleared before attempt-

ing to write to the device.

TRICKLE CHARGE REGISTER

This register controls the trickle charge characteristics

of the DS1302. The simplified schematic of Figure 5

shows the basic components of the trickle charger. The

trickle charge select (TCS) bits (bits 4 – 7) control the

selection of the trickle charger. In order to prevent acci-

dental enabling, only a pattern of 1010 will enable the

trickle charger. All other patterns will disable the trickle

charger. The DS1302 powers up with the trickle charger

disabled. The diode select (DS) bits (bits 2 – 3) select

whether one diode or two diodes are connected

between V

CC2

and V

CC1

. If DS is 01, one diode is

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