MCP795WXX/MCP795BXX SPI Real-Time Clock Calendar with Enhanced Features and Battery Switchover Device Selection Table User Memory: 32 kHz SRAM EEPROM Unique 64-Byte Battery-Backed SRAM Part Number Boot-up (Bytes) (Kbits) ID 2 Kbit and 1 Kbit EEPROM Memory: MCP795W20 No 64 2 Blank - Software block write-protect (, , or entire array) MCP795W10 No 64 1 Blank - Write Page mode (up to 8 bytes) MCP795W21 No 64 2 EUI-48 - Endurance: 1M erase/write cycles MCP795W11 No 64 1 EUI-48 128-Bit Unique ID in Protected Area of EEPROM: MCP795W22 No 64 2 EUI-64 - Available blank or preprogrammed MCP795W12 No 64 1 EUI-64 - EUI-48 or EUI-64 MAC address MCP795B20 Yes 64 2 Blank - Unlock sequence for user programming MCP795B10 Yes 64 1 Blank MCP795B21 Yes 64 2 EUI-48 Enhanced Features: MCP795B11 Yes 64 1 EUI-48 SPI Clock Speed up to 10 MHz MCP795B22 Yes 64 2 EUI-64 Programmable Watchdog Timer: MCP795B12 Yes 64 1 EUI-64 - Dedicated watchdog output pin Note: Watchdog Timer and Event Detects in all devices. - Dual retrigger using SPI bus or EVHS digital input Timekeeping Features: Dual Configurable Event Detect Inputs: Real-Time Clock/Calendar: - High-Speed Digital Event Detect (EVHS) with st th th nd - Hours, Minutes, Seconds, Hundredth of pulse count for 1 , 4 ,16 or 32 event Seconds, Day of Week, Month, Year, Leap - Low-Speed Event Detect (EVLS) with Year programmable debounce delays of 31 msec Crystal Oscillator requires External 32,768 kHz and 500 msec Tuning Fork Crystal and Load Capacitors. - Edge triggered (rising or falling) Clock Out Function: - Operates from VCC or VBAT - 1Hz, 4.096 kHz, 8.192 kHz, 32.768 kHz Operating Temperature Ranges: 32 kHz Boot-up Clock at Power-up (MCP795BXX) - Industrial (I Temp): -40C to +85C. 2 Programmable Alarms Supports IRQ or WDO Packages include 14-Lead SOIC and TSSOP Programmable open drain output Alarm or Interrupt Package Types (not to scale) On-Chip Digital Trimming/Calibration: SOIC/TSSOP - +/- 255 PPM range in 1 PPM steps X1 1 14 Vcc Power-Fail Time-Stamp Battery Switchover: - Logs time when VCC fails and VCC is restored X2 2 13 CLKOUT/BOOT VBAT 3 12 EVHS Low-Power Features: WDO 4 11 EVLS Wide Operating Voltage: IRQ 5 10 SCK -VCC: 1.8V to 5.5V CS 6 9 SI -VBAT: 1.3V to 5.5V VSS 7 8 Low Operating Current: SO -VCC Standby Current < 1uA 3V -VBAT Timekeeping Current: <700nA 1.8V Note: MCP795XXX is used in this document as a generic part number for the MCP795WXX, Automatic Battery Switchover from VCC to VBAT: MCP795BXX devices. - Backup power for timekeeping and SRAM retention 2011-2012 Microchip Technology Inc. Preliminary DS22280B-page 1 MCP795XXXMCP795WXX/MCP795BXX FIGURE 1-1: BLOCK DIAGRAM Description: The MCP795XXX is a low-power Real-Time Clock/ Calendar (RTCC) that uses digital trimming compen- sation for an accurate clock/calendar, an interrupt out- X1 VCC put to support alarms and events, a power sense circuit that automatically switches to the backup sup- OSC CLKOUT Divider ply, nonvolatile memory for safe data storage and sev- CLKOUT/ X2 BOOT eral enhanced features that support system requirements. V EVHS BAT Along with a low-cost 32,768 kHz crystal, this RTCC tracks time using several internal registers and then EEPROM communicates the data over a 10 MHz SPI bus that is WD EVLS fast enough to support a programmable millisecond alarm. ID WDT IRQ SCK The device is fully accessible through the serial inter- SRAM CC is between 1.8V and 5.5V, but can face, while V operate down to 1.3V through the backup supply con- CS SPI SDI nected to the VBAT input for timekeeping and SRAM TIME-STAMP retention only. As part of the power sense circuit, a time saver VSS SDO function is implemented to store the time when main power is lost and again, when power is restored to log the duration of a power failure. Along with the on-board serial EEPROM and battery- backed SRAM, a 128-bit protected space is available for a unique ID. This space can be ordered preprogrammed with a MAC address, or blank for the user to program. This clock/calendar automatically adjusts for months with fewer than 31 days including corrections for leap years. The clock operates in either 24-hour or 12-hour format with AM/PM indicator and settable alarm(s). Using the external crystal, the CLKOUT pin can be set to generate a number of output frequencies. In addition, the MCP795BXX devices support a 32 kHz clock output at power-up on the CLKOUT/BOOT pin by using the same crystal driving the RTCC device. For versatility, a digital event detect with a st th , 4 , programmable pulse count can identify the 1 th nd 16 or 32 pulse before sending an interrupt. A second event detect with built-in debounce input filter was also implemented to support noisy mechanical switches. Since many microcontrollers do not have an integrated Watchdog Timer, this peripheral has been imple- mented in the RTCC. For many applications, this function must be performed outside the microcontroller for increased robustness. DS22280B-page 2 Preliminary 2011-2012 Microchip Technology Inc. VBAT ALARMS SWITCHOVER EVENT DETECT