CDP68HC68T1M

Introduction

The CDP68HC68T1M device is a real time clock (RTC) that contains time of day, alarm and standard 13 interrupts. The clock features 16-bit divide-by-128 prescaler, two programmable 8-bit timers, two 8-bit counters and an internal oscillator. The device is available in 20 pin dual-in-line (DIP) and 28 pin microSOIC package.

Application Fields and Features

The CDP68HC68T1M RTC is ideal for applications requiring a combination of accurate time keeping and interrupt capability. Examples include PLCs, industrial automation, data acquisition, communication systems, and embedded systems. The device is software compatible with the Motorola MC68HC68T1M device. The CDP68HC68T1M features automatic leap year operation, 13 interrupts, crystal control circuitry, on-chip 1.2 volt regulator, and low battery detection. The device is designed for use with a 4.194304 MHz CMOS crystal for low power. The RTC operates over the industrial temperature range of -40°C to +85°C.

Working Principle

The CDP68HC68T1M RTC is powered by a 4.194304 MHz CMOS crystal that is connected to the XTAL1 and XTAL2 pins. When power is applied to the device, the oscillator is activated, and the crystal begins to oscillate at its designed frequency. The oscillator is maintained through the use of a transistor-based bias network that is driven by a 1.2 volt internal regulator. The regulator also maintains the device\'s logic levels and the 1.2 VCC voltage for CMOS logic cells.

The oscillator output is fed to a 16-bit divide-by-128 binary prescaler which provides the time base for the real time clock. The prescaler also provides an output enable signal to two 8-bit timers, two 8-bit counters, and an internal oscillator. The timing accuracy of the device is dependent upon the accuracy of the external crystal and the stability of the 1.2 VCC voltage.

The counting and timing rates of the two 8-bit timers and two 8-bit counters are software programmable. The count rate of the timers and counters can be adjusted to accommodate the application\'s requirements. The timers and counters can be used to provide independent real time or elapsed time measurements, which can be routed to various user selected output pins.

The timing accuracy of the CDP68HC68T1M RTC is also affected by temperature fluctuations. The device features an on-chip temperature compensation circuitry that minimizes timekeeping errors caused by temperature changes. This feature ensures that the device continues to keep accurate time even in erratic environmental conditions.

The CDP68HC68T1M RTC also features 13 interrupts that can be used to alert the processor of certain user selected events. The interrupts provide users with multiple options for scheduling software routines and program execution.

The CDP68HC68T1M RTC is ideal for applications requiring low power and accurate timekeeping capability. It is suitable for use in embedded systems, data acquisition systems, and industrial automation applications.

Conclusion

The CDP68HC68T1M is a low power real time clock (RTC). It contains time of day, alarm and standard 13 interrupts. The device is available in a 20 pin dual-in-line (DIP) and 28 pin microSOIC package. It features automatic leap year operation, crystal control circuitry, 1.2 volt on-chip regulator, low battery detection and temperature compensation. The CDP68HC68T1M is suitable for use in embedded systems, data acquisition systems, communication systems, and industrial automation systems.