On your device you MUST have everything (navcore and map) internal or on SD card as this cannot "switch between the two memories)
So...if there's no SD card it will boot/run from internal but if there's a full SD card (navcore/map) in when you start it it will boot/run from that card

Once you have your SDHC card loaded with navcore & map and copy of your ttgo.bif from internal then copy F/A onto the card & run this from your card reader