Using the DS87C530/DS5250 Real

文章摘要：Abstract: The Dallas Semiconductor DS87C530 high-speed microcontroller with real-time clock (RTC) is ideal for applications such as data logging. This application note examines temperature-measuring techniques interfacing to the DS1620 digital thermometer and thermostat. Time measurements and alarm

Using the DS87C530/DS5250 Real,标签：计算机控制技术,工厂电气控制技术,http://www.88dzw.com
Abstract: The Dallas Semiconductor DS87C530 high-speed microcontroller with real-time clock (RTC) is ideal for applications such as data logging. This application note examines temperature-measuring techniques interfacing to the DS1620 digital thermometer and thermostat. Time measurements and alarm settings using the DS87C530 are also discussed. Example code is included in this application note.

Overview

The DS87C530 and DS5250 incorporate a real-time clock (RTC) and alarm to allow the user to perform real-world timing operations such as time-stamping an event, performing a task at a specific time, or executing very long timing delays. Although software timing loops or internal timers could be used for such measurements, they are crystal dependent, inefficient for long time measurements, and are incompatible with the use of power management modes. Integration of the RTC means that only a 32.768kHz crystal is required. No load capacitors are required with the RTC crystal. The RTC is controlled by dedicated Special Function Registers (SFRs).

The RTC consists of subsecond, second, minute, hour, day of the week, and two total day count registers. In addition there is an alarm register for the subsecond, seconds, minutes, and hours registers. The subsecond register provides a resolution of 1/256 of a second and a maximum rollover count of 1 second. The registers and control bits used by the RTC are shown in Table 1. Bits and registers designated as unchanged after a reset may be indeterminate following a no-battery reset. Consult the full bit or register description for complete details.

Table 1. Real-Time Clock Control And Status Bit Summary

BIT NAME	LOCATION	FUNCTION	RANGE	RESET	READ/WRITE ACCESS
ERTCI	EIE.5	RTC Interrupt Enable		0	Unrestricted
PRTCI	EIP.5	RTC Interrupt Priority		0	Unrestricted
RTASS.7-0	RTASS	RTC Alarm Subsecond	0-FFh	Unchanged	Unrestricted
RTAS.5-0	RTAS	RTC Alarm Second	0-3Bh	Unchanged	Unrestricted
RTAM.5-0	RTAM	RTC Alarm Minute	0-3Bh	Unchanged	Unrestricted
RTAH.4-0	RTAH	RTC Alarm Hour	0-17H	Unchanged	Unrestricted
RTCSS.7-0	RTCSS	RTC Subsecond	0-FFh	Unchanged	Read: only if RTCRE=1. Cannot be written. Cleared when RTCWE 1<0
RTCS.5-0	RTCS	RTC Second	0-3Bh	Unchanged	Read: only if RTCRE=1. Write: only if RTCWE=1. 1ms Read/Write window
RTCM.5-0	RTCM	RTC Minute	0-3Bh	Unchanged
RTCH.4-0	RTCH.4-0	RTC Hour	0-17h	Unchanged
DOW2-0	RTCH.7-5	RTC Day of Week	0-7h	Unchanged
RTCD1.7-0 RTCD0.7-0	RTCD1, (MSB) RTCD0, (LSB)	RTC Day	0-FFFFh	Unchanged
SRCE	RTCC.7	RTC Subsecond Compare enable		Unchanged	Unrestricted
SCE	RTCC.6	RTC Second Compare Enable		Unchanged	Unrestricted
MCE	RTCC.5	RTC Minute Compare Enable		Unchanged	Unrestricted
HCE	RTCC.4	RTC Hour Compare Enable		Unchanged	Unrestricted
RTCRE	RTCC.3	RTC Read Enable		0	Unrestricted
RTCWE	RTCC.2	RTC Write Enable		0	Read: Unrestricted Write: Timed Access
RTCIF	RTCC.1	RTC Interrupt Flag		0	Unrestricted
RTCE	RTCC.0	RTC Enable		Unchanged	Read: Unrestricted Write: Timed Access
E4K	TRIM.7	External 4096Hz RTC Signal Enable		0
X12/ /6\	TRIM.6	RTC Crystal Capacitance Select		Unchanged
TRM2-0	TRIM.5 TRIM.3 TRIM.1	RTC Trim Bit 2-0		Unchanged	Read: Unrestricted Write: Timed Access
/0 - TRM2\	TRIM.4 TRIM.2 TRIM.0	RTC Inverted Trim Bit 2-0		Unchanged	Read: Unrestricted Write: Timed Access Must be inverse of TRM2-0

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