EG91 sleep mode

Hi Forum,
I am using a EG91 module and communicating with it over the uart.
I have successfully put the module to sleep by raising the DTR line and it wakes up via a URC or dropping the DTR line.

Our software needs to occasionally wake the module by dropping the DTR line to carry out various functions. Although this works, there is an understandable delay between dropping the DTR line and the module waking up and being ready to accept AT commands. Through trial and error I have determined this delay to be around 8ms.

I was wondering if there is another way of detecting when the module is fully awake and ready to accept AT commands? I cannot see anything obvious, but hopefully there is something that i have missed.
Alternatively does anyone know what the maximum wakeup time is?

Many thanks
Alan