Signal aquisition using LTC2255IUH 14bit 125MHz ADC, and Artix-7 FPGA DDR3 Core Board

I need to get 5 miliseconds data (625000 values of 14 bit each), each time I press a button B1, until DDR3 memory is full. The B1 button must be usable again only after the 5ms of data storing ended. An index counter must be incremented with 625000. If I press a button B2, data must be sent to UART at 115200 baudrate, from memory index 0 to current index (multiples of 625000). The index will NOT be resetted, so the B2 button can be pressed as many time as needed, to download data. Data sent to UART must be encoded like this: 0 (not used zero) + 0 (not used zero) + 14bit ADC data from DDR3 = 16 bits And the sending: MSB 8bit + LSB 8bit + CHECKSUM8(MSBLSB) + \n uint8 + uint8 + uint8 + \n After each 1000 octets sent to UART a small delay must be inserted (we test the delay time), so that the PC buffer don't get overflow. If I press a button B3, the index counter reset to zero, so I can start again storing data. The aquisition speed is 125Msps, at 14bit.