Hi Eric, >The Dallas Semiconductor "Nonvolatile Timekeeping RAM" found in many popular controllers, including the Link RLC-1 Plus, is Part Number DS1643-150. We have a lot of experience with the DS1643 and its bigger brother, the DS1644. The S-COM 5K uses the DS1643 (8K RAM), and the 6K and 7K use the DS1644 (32K RAM). A second source for the DS1643 is the STMicro M48T18-100PC1. For the DS1644, a second source is the STMicro M48T35Y-70PC1. >Notice that the "-150" indicates 150 ns access time. The replacement device offered by Dallas/Maxim has either 70 ns or 100 ns access time, and I have no idea if the newer device will work properly where a 150 ns device was used.
As a rule, a faster memory is okay. Slower isn't. >I see that the guaranteed accuracy of the DS1643 clock is within +/- 1 minute per month, and there is no capability to tweak the crystal to get better accuracy. That's right. We've been using these parts for many years and the reports from the field range from excellent to mediocre timekeeping. The controllers have "clock tweak" commands that add or subtract seconds and can be called from the scheduler program. If one knows how many seconds the clock is gaining or losing in a day, then automatically resetting the clock daily (or more often) makes for a pretty accurate clock. Dallas/Maxim now has a series of timekeeping ICs and temperature compensated crystal oscillators. We're using the DS32KHZ TCXO in the new 7330 with good results, so perhaps the temperature at the repeater site has a lot to do with the accuracy of the controller's clock and calendar. 73, Bob Bob Schmid, WA9FBO, Member S-COM, LLC PO Box 1546 LaPorte CO 80535-1546 970-416-6505 voice 970-419-3222 fax www.scomcontrollers.com ************************************** See what's new at http://www.aol.com
