A multi-mode radio communications device 100 provides simultaneous timebase monitoring for GSM/TDMA/EDGE using Accumulator Type 'Layer 1' timers (150) to avoid the need for one or more secondary reference phase lock loops (PLLs). The use of such timers allows achievement by only digital means of GSM and TDMA synchronization requirements without using additional dedicated reference PLLs, as well as saving multiple integrated circuit (IC) pins and several external components. Also, through the use of such timers, no real time software adjustment is required. This provides the following further advantages: support of simultaneous multi-mode; low part count and cost savings; fast recovery from DEEP SLEEP MODE due to the settling time of the crystals only; and simplification of multi-mode DEEP SLEEP MODE since only one single crystal clock frequency relation needs to be tracked rather various clocks frequencies; and simplification of digital signal processing by allowing sharing of the same hardware resources for all modes since those hardware resources are clocked with one clock source derived from one reference clock with maintained synchronization.