Content for DS1387


The DS1385/DS1387 RAMified Real Time Clocks (RTCs) are upward–compatible successors to the industry standard DS1285/DS1287 RTC’s for PC applications. In addition to the basic DS1285/DS1287 RTC functions, 4K bytes of on–chip nonvolatile RAM have been added. The RTC functions include a time–of–day clock, a onehundred year calendar, time–of–day interrupt, periodic interrupts, and an end–of–clock update cycle interrupt. In addition, 50–bytes of user NV RAM are provided within this basic RTC function which can be used to store configuration data. The clock and user RAM are maintained in the absence of system VCC by a lithium battery. The 4K x 8 additional NV RAM is provided to store a much larger amount of system configuration data than is possible within the original 50–byte area. This RAM is accessed via control signals separate from the RTC, and is also maintained as nonvolatile storage from the lithium battery.

Replacing a dead lithium cell in the DS1387

“While most PCs use a RTC/CMOS chip that has an external battery, many industrial x86 computers use RTC/NVRAM modules. They’re convenient when new, since the battery and RTC crystal are encapsulated into the module. The module’s …