Serial Real-Time Clock/Calendar Low-Cost Timekeeping Solution Summary Microchip’s portfolio of Real-Time Clock/Calendars (RTCCs) offer low-cost system timekeeping solution. RealTime Clock/Calendars track time with resolutions as small as 1/100th of a second and issue alarms on a wide variety of time conditions. The RTCC maintains accurate time through system shutdowns by automatically switching over to an external battery back-up source. RTCC’s are designed to operate using a 32.768 kHz quartz crystal and can digitally compensate for frequency variance caused by crystal tolerance and temperature. Microchip RTCC’s have a I2C™ or SPI interface for configuration, reading and writing the time. Additionally, alarm interrupt requests, square wave output and system reset control signals are available on dedicated pins. Microchip’s RTCCs are available with a range of internal memories including battery-backed SRAM, non-volatile EEPROM and an additional area of protected EEPROM. The protected EEPROM area is only writable after the RTCC receives an unlock sequence and is available pre-programmed with unique EUI-48™ or EUI-64™ MAC address. Custom programming is also available. SRAM Transition count event detection* EEPROM Interrupt or Alarm Debounced input* Time Stamp System Controller System reset* Event Handler WDT Timekeeping Serial Interface *Optional Available Reference Materials ■■ ■■ ■■ ■■ ■■ ■■ ■■ ■■ Hardware design guidance Circuit schematics and gerber files Characterized crystal recommendations Code examples Migration guides Configuration directions Debugging guides User support forum Key Features and Benefits Features Benefits Automated timekeeping Offload timekeeping tasks, including leap year management to the RTCC Dual alarms System controller can attend to other tasks and have the RTCC indicate a specific time has been reached Battery back-up Maintain time through system powerdowns and preserve SRAM contents Time stamp Capture the time when system power was lost and restored Versatile clock-out/alarm/output pin The RTCC can produce a squarewave for the system, or wake a processor from a low-power state on a time match to indicate an alarm has occurred 64-bytes battery backed SRAM Unlimited endurance non-volatile data storage for data that needs to be maintained through a shutdown Digital oscillator trimming/calibration Adjust for crystal frequency tolerance and drift to maintain accurate time Up to 128-bit protected EEPROM area Robust non-volatile storage. Only writable after an unlock sequence Pre-programmed EUI MAC ID Unique identifier in every device which can be used as a serial number or as a network MAC ID. Using a preprogrammed MAC ID avoids the expense of purchasing an ID block and serialized programming Up to 2 Kb general purpose EEPROM Long-term storage of parameters, system modes, calibration information and data through shutdowns Watch-dog timer Guards against the controller software getting trapped in a loop or awaiting an event Debounced input event detect Places the system controller in a low-power state and has the RTCC detect a true event from a noisy sensor Transition count event detect The RTCC can alert the system once it records a specific number of logic-level transitions on a signal, allowing monitoring to be delegated to the RTCC Low-Cost Real-Time Clock Calendar Portfolio Pins Interface Battery Back-up Protected EEPROM Area (bits) Protected EEPROM Contents General Purpose EEPROM (Kbits) Watchdog Timer and Event Detects 8 I2C™ – – N/A – – 8 2 IC ü – N/A – – MCP79400 8 2 IC ü 64 – – – MCP79401 8 I2C ü 64 EUI-48 – – 8 2 IC ü 64 EUI-64 – – MCP79410 8 2 IC ü 64 – 1 – MCP79411 8 I2C ü 64 EUI-48 1 – MCP79412 8 2 IC ü 64 EUI-64 1 – MCP79510 10 SPI ü 128 – 1 – Product MCP7940M MCP7940N MCP79402 MCP79511 10 SPI ü 128 EUI-48 1 – MCP79512 10 SPI ü 128 EUI-64 1 – MCP79520 10 SPI ü 128 – 2 – MCP79521 10 SPI ü 128 EUI-48 2 – MCP79522 10 SPI ü 128 EUI-64 2 – MCP795W10 14 SPI ü 128 – 1 ü MCP795W11 14 SPI ü 128 EUI-48 1 ü MCP795W12 14 SPI ü 128 EUI-64 1 ü MCP795W20 14 SPI ü 128 – 2 ü MCP795W21 14 SPI ü 128 EUI-48 2 ü MCP795W22 14 SPI ü 128 EUI-64 2 ü Power-Fail Time-Stamp Development Tools from Microchip Supply Voltage To support our Real-Time Clock/Calendar products, we offer two PICtail™ daughter boards, each with a characterized crystal oscillator circuit and an on-board coin cell battery for use as a back-up supply. Compatible code development platforms include the PICDEM™ PIC18 Explorer Board (DM183032) and the Explorer 16 Development Board (DM240001). Loss of system power Battery back-up switch over voltage Time Time captured by power-fail timestamp Time captured by power-up timestamp MCP79410 RTCC PICtail Plus Daughter Board (AC164140) MCP795XX RTCC PICtail Daughter Board (AC164147) www.microchip.com/clock Visit our web site for additional product information and to locate your local sales office. Microchip Technology Inc. • 2355 W. Chandler Blvd. • Chandler, AZ 85224-6199 Information subject to change. The Microchip name and logo and the Microchip logo are registered trademarks and PICDEM and PICtail are trademarks of Microchip Technology Incorporated in the U.S.A. and other countries. All other trademarks mentioned herein are property of their respective companies. © 2014, Microchip Technology Incorporated. All Rights Reserved. Printed in the U.S.A. 7/14 DS20005074B