The CDP68HC68T1 Real-Time Clock provides a time/calendar function, a 32 byte static RAM, and a 3 wire Serial Peripheral Interface (SPI Bus). The primary function of the clock is to divide down a frequency input that can be supplied by the on-board oscillator in conjunction with an external crystal or by an external clock source. The internal oscillator can operate with a 32kHz, 1MHz, 2MHz, or 4MHz crystal. An external clock source with a 32kHz, 1MHz, 2MHz, 4MHz, 50Hz or 60Hz frequency can be used to drive the CDP68HC68T1. The time registers hold seconds, minutes, and hours, while the calendar registers hold day-of-week, date, month, and year information. The data is stored in BCD format. In addition, 12 or 24 hour operation can be selected. In 12 hour mode, an AM/PM indicator is provided. The T1 has a programmable output which can provide one of seven outputs for use elsewhere in the system. Computer handshaking is controlled with a wired-OR interrupt output. The interrupt can be programmed to provide a signal as the result of:

  1. An alarm programmed to occur at a predetermined combination of seconds, minutes, and hours.
  2. One of 15 periodic interrupts ranging from sub-second to once per day frequency.
  3. A power fail detect. The PSE output and the VSYS input are used for external power control. The CPUR output is available to reset the processor under power-down conditions. CPUR is enabled under software control and can also be activated via the CDP68HC68T1's watchdog. If enabled, the watchdog requires a periodic toggle of the CE pin without a serial transfer.


  • SPI (Serial Peripheral Interface)
  • Full Clock Features
  • Seconds, Minutes, Hours (12/24, AM/PM), Day of Week, Date, Month, Year (0 to 99), Automatic Leap Year
  • 32 Wordx8-Bit RAM
  • Seconds, Minutes, Hours Alarm
  • Automatic Power Loss Detection
  • Low Minimum Standby (Timekeeping) Voltage 2.2V
  • Selectable Crystal or 50/60Hz Line Input
  • Buffered Clock Output
  • Battery Input Pin that Powers Oscillator and also Connects to VDD Pin When Power Fails
  • Three Independent Interrupt Modes
  • Alarm
  • Periodic
  • Power-Down Sense
  • Pb-Free Available (RoHS Compliant)

Product Options

Part Number Part Status Pkg. Type Carrier Type MOQ Buy Sample
Active PDIP Tube 500
Active SOICW Tube 480
Active SOICW Reel 1000
Active SOICW Tube 380
Active SOICW Reel 1000

Documentation & Downloads

Title language Type Format File Size Date
Datasheets & Errata
CDP68HC68T1 Datasheet Datasheet PDF 1.04 MB
Application Notes & White Papers
AN9766: Keeping Time with the Intersil CDP68HC68T1 Real Time Clock and the Millennium Bug Application Note PDF 554 KB
PCN13060 - Test Site Change for the Listed Intersil Products Product Change Notice PDF 223 KB
PCN12094 - Alternate Manufacturing Site for Assembly of the Listed Intersil Packaged Products - Amkor Technology, Philippines (ATP) Product Change Notice PDF 98 KB
PCN12086 - Alternate Manufacturing Site for Assembly of the Listed Intersil PDIP Packaged Products -Amkor Technology, Philippines (ATP) Product Change Notice PDF 86 KB
PIN19006 - Price Increase for the Listed Renesas Electronics America Products Price Increase Notice PDF 257 KB
Semiconductor Package Mount Manual 日本語, 简体中文 Other PDF 10.28 MB
PIN17006 - Q1 2017 Price Increase Price Increase Notice PDF 227 KB
Semiconductor Reliability Handbook 日本語 Other PDF 14.70 MB
QFN Mounting Manual 日本語, 简体中文 Other PDF 3.19 MB