# Is there a minimum wake time (ST) when using synchronous sleep mode? **URL:** \ **Category:** XBee - DigiMesh\ **Tags:** sleep, time, xbee-sleep, wake, minimum\ **Created:** [August 31, 2016, 9:29am UTC](https://forums.digi.com/t/is-there-a-minimum-wake-time-st-when-using-synchronous-sleep-mode/17320 "2016-08-31T09:29:11Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![flavia](https://avatars.discourse-cdn.com/v4/letter/f/a87d85/32.png) [@flavia](https://forums.digi.com/u/flavia)\ **Post date:** [August 31, 2016, 9:29am UTC](https://forums.digi.com/t/is-there-a-minimum-wake-time-st-when-using-synchronous-sleep-mode/17320/1 "2016-08-31T09:29:11Z")
Hi! We are using XBee 868 to connect to sensors, some of which are on battery, so we want to minimize the power use. When building a mesh network (so we set the XBee’s to synchronous sleep mode, SM 8 or SM 7), we try to set the wake time (ST) as short as possible. It seems like there is a minimum wake time, because when we try to set it to less than 3 seconds it just sets it back to the same value (CA5, or 3237 ms). The same is true if I try to set it via AT commands. But I haven’t found anything in the documentation stating a minimum wake time for synchronous sleep modes. With asynchronous sleep modes we have no problem setting the wake mode to shorter values than this. Thanks in advance, Flavia ---
**Author:** ![NicholasWilson](https://avatars.discourse-cdn.com/v4/letter/n/c77e96/32.png) [@NicholasWilson](https://forums.digi.com/u/NicholasWilson)\ **Post date:** [August 31, 2016, 10:08am UTC](https://forums.digi.com/t/is-there-a-minimum-wake-time-st-when-using-synchronous-sleep-mode/17320/2 "2016-08-31T10:08:11Z")
868 LP I assume as 868 Pro has been end of lifed. Page 69 of the manual is what you are looking for: The ST parameter will automatically adjust upwards to its minimum value when other AT commands are changed that will affect it (SP, and NH). ---
**Author:** ![mvut](https://sea2.discourse-cdn.com/flex016/user_avatar/forums.digi.com/mvut/32/31_2.png) [@mvut](https://forums.digi.com/u/mvut)\ **Post date:** [August 31, 2016, 2:32pm UTC](https://forums.digi.com/t/is-there-a-minimum-wake-time-st-when-using-synchronous-sleep-mode/17320/3 "2016-08-31T14:32:04Z")
Close. The NH, BH, and SP time that control the min wake cycle time.