Problems and Solutions for Adj
abstract: recent u.s. legislation increased the daylight saving time (dst) period by four weeks. this change will affect systems that adjust for dst by using real-time clocks (rtcs) with an integrated dst adjustment. this note discusses issues related to the dst change, shows how to test and adjust the rtc for dst, and recommends how to manage dst in future designs.
introduction and background on dst implementationsince 1986 daylight saving time, in the u.s., begins on the first sunday in april and ends on the last sunday in october. canada and mexico also follow this schedule¹. beginning in 2007, however, daylight saving time in the u.s. will begin on the second sunday in march and end on the first sunday in november².
historically the ds1287 rtc, used on the ibm at personal computer (pc), integrated the u.s. dst function. if the dst function was enabled, the operation system's (os) clock used the time and date information from the rtc at boot time to reflect the proper time. for legacy reasons, all other dallas semiconductor multiplexed-bus interface rtcs also support the dst function. (see table 1.)
table 1. multiplexed-bus rtcs with integrated dst operation ds12885/87 ds12r885/cr887/r887 ds14285/87
ds1685/87 ds1688/91 ds1689/93
ds17285/87 ds17485/87 ds17885/87
in modern operating systems the os, not the rtc, handles the dst function. since dst is implemented differently worldwide and can change often, using the os allows relatively easy updates to the dst function and dst support. embedded systems, in contrast, often have limited software, firmware, or memory resources, are limited to sales in north america, and may still implement dst by using the rtc's integrated dst function.
the dst function is important in some applications where there is no os dst adjustment. traffic signal controllers, for example, adjust the signal timing during morning and evening rush hours, which shift with dst. other applications, such as fax machines, may depend upon the user to input the correct time when a dst shift occurs, and therefore have little need for automatic dst adjustment. recommendations for managing dst adjustmentsat this time dallas semiconductor does not plan to change the dst function on the multiplexed-bus product line. we encourage customers whose applications depend on proper adjustment to dst to update their products so that firmware handles dst changes, not the rtc.
meanwhile, if you are managing changes for dst with an rtc, the figure 1 flowchart will help you. it shows the basic steps required to test and adjust for dst. when adjusting back to standard time in november, a flag must be used to determine if the shift from 2:00am to 1:00am already occurred. this bit should be nonvolatile in case a power failure occurs in the hour after time has been reset to 1:00am. a bit in one of the rtc's general-purpose battery-backed registers could be used for this purpose. conclusionnew designs should implement the dst function in firmware or software. by doing so, adjustments for changes in the dst schedule are more easily implemented.
figure 1. flowchart of the basic steps to test and adjust for dst with an rtc.
notes states and provinces within the u.s., mexico, and canada choose to observe dst depending on local laws. canada will adhere to the new u.s. dst schedule in 2007. as of this writing, it is not known whether mexico will follow.
美能达3170维修代码
垂直轴小型风力发电机与水平轴小型风力发电机对比
自制pcb需要注意哪一些点
S7-300 PLC在变电站中的应用
Intel下一代核心i3 CPU将在台积电5nm工艺上生产
Problems and Solutions for Adj
2018年深圳国际电路板采购展即将开始,CS show 2018同期论坛四大看点
创新型焊接桥式整流器，提高电子产品生产工艺！
了解RISC OS桌面开源操作系统的基础知识
数字资产量化交易系统开发自动交易软件开发
怎样用Python制作迷宫GIF 本文将告诉你诀窍
C语言函数宏怎样实现封装呢？
电气工程施工主要流程的工艺解读
协作机器人的的概念首先应是好用而不是便宜
车载液晶电视显示器专用MCU及设计方案
物联网遭受到网络攻击怎么解决
生成式AI是更大的机会，开始行动是关键
荣耀Note9什么是上市？华为荣耀Note9发布时间撞车华为Mate10，搭载麒麟965+6.6英寸超大全面屏
【节能学院】矿山井下IT配电系统绝缘监测研究及应用
中国联通5G MiFi和5G CPE
introduction and background on dst implementationsince 1986 daylight saving time, in the u.s., begins on the first sunday in april and ends on the last sunday in october. canada and mexico also follow this schedule¹. beginning in 2007, however, daylight saving time in the u.s. will begin on the second sunday in march and end on the first sunday in november².
historically the ds1287 rtc, used on the ibm at personal computer (pc), integrated the u.s. dst function. if the dst function was enabled, the operation system's (os) clock used the time and date information from the rtc at boot time to reflect the proper time. for legacy reasons, all other dallas semiconductor multiplexed-bus interface rtcs also support the dst function. (see table 1.)
table 1. multiplexed-bus rtcs with integrated dst operation ds12885/87 ds12r885/cr887/r887 ds14285/87
ds1685/87 ds1688/91 ds1689/93
ds17285/87 ds17485/87 ds17885/87
in modern operating systems the os, not the rtc, handles the dst function. since dst is implemented differently worldwide and can change often, using the os allows relatively easy updates to the dst function and dst support. embedded systems, in contrast, often have limited software, firmware, or memory resources, are limited to sales in north america, and may still implement dst by using the rtc's integrated dst function.
the dst function is important in some applications where there is no os dst adjustment. traffic signal controllers, for example, adjust the signal timing during morning and evening rush hours, which shift with dst. other applications, such as fax machines, may depend upon the user to input the correct time when a dst shift occurs, and therefore have little need for automatic dst adjustment. recommendations for managing dst adjustmentsat this time dallas semiconductor does not plan to change the dst function on the multiplexed-bus product line. we encourage customers whose applications depend on proper adjustment to dst to update their products so that firmware handles dst changes, not the rtc.
meanwhile, if you are managing changes for dst with an rtc, the figure 1 flowchart will help you. it shows the basic steps required to test and adjust for dst. when adjusting back to standard time in november, a flag must be used to determine if the shift from 2:00am to 1:00am already occurred. this bit should be nonvolatile in case a power failure occurs in the hour after time has been reset to 1:00am. a bit in one of the rtc's general-purpose battery-backed registers could be used for this purpose. conclusionnew designs should implement the dst function in firmware or software. by doing so, adjustments for changes in the dst schedule are more easily implemented.
figure 1. flowchart of the basic steps to test and adjust for dst with an rtc.
notes states and provinces within the u.s., mexico, and canada choose to observe dst depending on local laws. canada will adhere to the new u.s. dst schedule in 2007. as of this writing, it is not known whether mexico will follow.
美能达3170维修代码
垂直轴小型风力发电机与水平轴小型风力发电机对比
自制pcb需要注意哪一些点
S7-300 PLC在变电站中的应用
Intel下一代核心i3 CPU将在台积电5nm工艺上生产
Problems and Solutions for Adj
2018年深圳国际电路板采购展即将开始,CS show 2018同期论坛四大看点
创新型焊接桥式整流器，提高电子产品生产工艺！
了解RISC OS桌面开源操作系统的基础知识
数字资产量化交易系统开发自动交易软件开发
怎样用Python制作迷宫GIF 本文将告诉你诀窍
C语言函数宏怎样实现封装呢？
电气工程施工主要流程的工艺解读
协作机器人的的概念首先应是好用而不是便宜
车载液晶电视显示器专用MCU及设计方案
物联网遭受到网络攻击怎么解决
生成式AI是更大的机会，开始行动是关键
荣耀Note9什么是上市？华为荣耀Note9发布时间撞车华为Mate10，搭载麒麟965+6.6英寸超大全面屏
【节能学院】矿山井下IT配电系统绝缘监测研究及应用
中国联通5G MiFi和5G CPE