The Real-Time Clock Has The Ability To Calculate Seconds, Minutes, Hours, Days, Weeks, Months, And Years Before 2100, As Well As The Ability To Adjust For Leap Years; 31 8-Bit Temporary Data Storage Ram; Serial I/O Port Mode Minimizes The Number Of Pins; Wide Range Of Operating Voltage 2.0 To 5.5v; When The Operating Current Is 2.0v, It Is Less Than 300na; When Reading/Writing Clock Or Ram Data, There Are Two Transmission Methods: Single- Transmission And Multi- Transmission ; 8-Pin Dip Package Or Optional 8-Pin Soic Package Based On Surface Mount; Simple 3-Wire Interface; Compatible With Ttl Vcc=5v; Industrial Temperature Range -40 - +85; Dual Power Tubes For Main Power Supply And Backup Power Supply;<br><br>1. Pcb Is A Single Panel, Size: About 44mm x 23mm x 1.6mm 2. With 4 Positioning Holes, Diameter 3.1mm 3. The Backup Battery Is CR2032(Without), Voltage 3v, Current 260mah, Non-Rechargeable Battery. The Theoretical Data Retention Time Is 10 Years! 4. Crystal Oscillator 32.768khz, Crystal Oscillator From Japan, Matching Capacitance Is 6pf, Size 2x6mm 5. Ds1302 Is An 8-Pin Direct-Plug Domestic Large Chip. There Is An Ic Holder Under The Chip To Facilitate The Replacement And Insertion Of The Chip. 6. The Module Working Voltage Is Compatible With 3.3v/5v And Can Be Connected To 5v And 3.3v Microcontrollers. 7. Wiring (Take The Provided Program As An Example, You Can Connect Any Io Port, Just Modify The Port Definition In The Program): VCC+5V/3.3V GNDGND CLKP02 DATP01 P00 Note: Never Connect VCC And Gnd In Reverse To Avoid Burning Out The Chip. The P0 Port Of The 2.51 Microcontroller Needs To Be Connected To A Pull-Up Resistor. If Your Microcontroller Does Not Have A Pull-Up Resistor, You Can Connect The Data Line To Other Ports. Different Batches May Have Differences In Product Appearance, Color, And Printed Characters, Which Will Not Affect The Use. Colour:As Shown Material:PCB<br><br>Package Contents: 20 * Clock Modules<br><br>Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.