The GW-1742-1 is a complete replacement for the Dallas DS1742 RTC/NVRAM. This replacement module is designed using modern low-power components and a newer controller than used in the original DS1742, but is 100% electrically compatible with the originals. The software interface is identical, except for the low battery test function, which is not implemented (bit 7 of address 0x7FC). This small difference does not cause operating problems in the systems we've tested, and the bit can be set to 1 if desired (battery good indication).

These 5V RTC/NVRAM modules are also compatible with "old style" ST/Mostek M48T02 NVRAMs, used in many 80s and 90s UNIX systems, such as the sun4/sun4c series of computers. They provide register level compatibility and will physically fit in the extractors used with Suns.

Do note that these modules (green) are 5V devices, the GW-1742W-1 (blue) is the 3.3V version! The GW-1742-1 will appear to function in 3.3V systems, but writes will be inhibited. The GW-1742-1 can be read and written using programmers such as the common TL866+. Programmers that do not support the RTC section of the module may throw programming or checksum errors.

The GW-1742-1 consists of a small circuit board, low-power SRAM, Dallas/Maxim RTC and NVRAM controller, and CR1225 battery. The circuit board uses Batten & Allen leadframe pins, making it compatible with even single-wipe sockets, while also keeping module height to a minimum. The GW-1742-1 is actually slightly shorter than the original Dallas modules, despite using a coin cell holder.

The GW-1742-1 is maintainable: the CR1225 lithium cell (included) can be removed from the cell holder and replaced with the system powered up, preventing loss of NVRAM contents. All GW-1742-1 modules are built with 100% new components sourced from reputable distributors, and are fully tested for RTC and NVRAM functionality. Like all of our products, the GW-1742-1 is designed and made in the USA.