CMOS Serial Real-Time Clock With RAM And Power Sense/Control

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: An alarm programmed to occur at a predetermined combination of seconds, minutes, and hours. One of 15 periodic interrupts ranging from sub-second to once per day frequency. 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 CDP68HC68T1s watchdog. If enabled, the watchdog requires a periodic toggle of the CE pin without a serial transfer.
By Intersil Corporation