Default [Q] Samsung Tab 10.1 no fastboot mode

I am trying to build my own rom from the AOSP source however I cannot flash it because fastboot does not recognise my device. I have a Samsung Tab 10.1 (GT-P7500) 3G/Wifi. When I try rebooting it and holding down power and volume down I get two options: recovery and downloading mode, there is no 'fastboot' mode. Is there any way I can get fastboot mode onto my device? I have tried searching everywhere but I have yet to yield any solution. Thank you!