# XBee S2 problem **URL:** \ **Category:** XBee - Zigbee\ **Created:** [September 6, 2011, 11:50am UTC](https://forums.digi.com/t/xbee-s2-problem/757 "2011-09-06T11:50:49Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![LaurenPan](https://avatars.discourse-cdn.com/v4/letter/l/2bfe46/32.png) [@LaurenPan](https://forums.digi.com/u/LaurenPan)\ **Post date:** [September 6, 2011, 11:50am UTC](https://forums.digi.com/t/xbee-s2-problem/757/1 "2011-09-06T11:50:49Z")
Hello friends, I am using two XBee S2 module for my own project. But I can’t figure out why there is a delay when the router received data from a coordinator. Here is the configuration for my two XBee modules. One: Modem: XB24-ZB Function set: Zigbee coordinator AT version 208C PAN ID: 27 SC: FF The other: Modem: XB24-ZB Function set: Zigbee Router AT version 228C PAN ID: 27 SC: FF When the router transmit data to the coordinator, it works well. The coordinator could receive it and display the data in the Serial monitor. But when I want to transmit data from a coordinator to a router, the Serial monitor couldn’t get the data at the same time. Maybe several seconds later, it displayed. I don’t know what cause the delay. Any suggestions will be helpful. Thanks a lot. Regards, Lauren ---
**Author:** ![lynnl](https://avatars.discourse-cdn.com/v4/letter/l/22d042/32.png) [@lynnl](https://forums.digi.com/u/lynnl)\ **Post date:** [September 8, 2011, 11:57am UTC](https://forums.digi.com/t/xbee-s2-problem/757/2 "2011-09-08T11:57:50Z")
I always use API on coordinator, so don’t have any experience with an AT-mode coordinator. My first guess is the coordinator is always doing route discovery, whereas the router is remembering that it can talk directly to the coordinator (they use a different algorithm). The route-discovery involves a broadcast (much like an IP ‘ARP’) asking who knows how to reach the IEEE MAC address. This takes up to 5 second to complete. I don’t know how to speed up the process.