テストに使ったプログラムの抜粋です

int __fastcall TForm2::FifoOpen()
{
    FT_STATUS ftStatus;
    int serial_length;
	DWORD InTransferSize  =65535;
	DWORD OutTransferSize =4096;
    char *serial;
    serial = "HDL00511A";
    int ret;

    ret = -1;

	for(;;){

		ftStatus = FT_OpenEx(serial, FT_OPEN_BY_SERIAL_NUMBER, &handle);
        if(ftStatus != FT_OK){
                AddMemo("FT_OPEN_BY_SERIAL_NUMBER : NG");
                break;
        }else{
                AddMemo("FT_OPEN_BY_SERIAL_NUMBER : OK");
        }

        ftStatus = FT_SetBitMode(handle, 0, 0x40);
        if(ftStatus != FT_OK){
                AddMemo("FT_SetBitMode(Sync-FIFO Mode) : NG");
                break;
        }else{
                AddMemo("FT_SetBitMode(Sync-FIFO Mode) : OK");
        }

        ftStatus = FT_SetLatencyTimer(handle, 2);
		if(ftStatus != FT_OK){
                AddMemo("FT_SetLatencyTimer : NG");
				break;
        }else{
                AddMemo("FT_SetLatencyTimer : OK");
        }

		ftStatus = FT_SetUSBParameters(handle, InTransferSize, OutTransferSize);

		 if(ftStatus != FT_OK){
				AddMemo("FT_SetUSBParameters : NG");
				break;
		}else{
				AddMemo("FT_SetUSBParameterse : OK");
		}
		ftStatus = FT_SetFlowControl( handle, FT_FLOW_RTS_CTS, 0x10,0x13);

		 if(ftStatus != FT_OK){
				AddMemo("FT_SetFlowControl : NG");
				break;
		}else{
				AddMemo("FT_SetFlowControl : OK");
		}
		// 正常リターン
        ret = 0;
        break;

    }
    if( ret == 0 ){
        AddMemo("FIFO OPEN : OK");
    }else{
         AddMemo("FIFO OPEN : NG");
    }
    return ret;
}



int __fastcall TForm2::Write_1000( char *p, int len, int kaisuu )
{
FT_STATUS ftStatus;
DWORD writtenBytes;
int ret;
    ret = 0;
    for( int ii=0; ii < kaisuu; ii++ ){

        ftStatus = FT_Write(handle, p, len, &writtenBytes);
        if(ftStatus != FT_OK){
            ret = -1;
            break;
        }

    }
    return  ret;

}

// 送信テスト
int __fastcall TForm2::FifoExam_snd( void )
{
String str;
FT_STATUS ftStatus;
DWORD writtenBytes;
DWORD EventDWord;
DWORD TxBytes;
DWORD RxBytes;
DWORD BytesReceived;
char *RxData;
char *TxData;
String DiffTime;
long fDiffTIme;
long totalbyte;
long nn;
int kaisuu;
int ret;
    AddMemo("送信テスト");
    gExamBurden = Edit_ExamBurden->Text.ToInt();

    TxData = new char[gExamBurden+1];    //*1

    for(int i=0; i<gExamBurden; i++){
        TxData[i] = '0' + i%(16*3-1);
    }
    TxData[gExamBurden] = '\0';

    kaisuu = 10;
	ret = -1;
    for(;;){

        QueryPerformanceCounter(&gStartTime); //開始時間

        if( Write_1000(TxData, gExamBurden, kaisuu)!= FT_OK){
                AddMemo("FT_Write ERROR");
                break;
        }

        QueryPerformanceCounter(&gEndTime);  //終了時間

        fDiffTIme = ((gEndTime.QuadPart - gStartTime.QuadPart)*1000 / gCpuFreq.QuadPart);
        DiffTime.sprintf("%d [mSec]", (DWORD)fDiffTIme);
        AddMemo( DiffTime ) ;

        totalbyte =  gExamBurden * kaisuu;
        nn = 1000*(totalbyte / (fDiffTIme+0.0000000001));
        String tmp;
        tmp.sprintf( "%d bytes---%6.3f [MBytes/sec] " ,totalbyte,  (float)nn/1000000.0 );
        AddMemo( tmp  ) ;


		ret = 0;
        // 正常終了
        break;

    }
    AddMemo("................");
    delete [] TxData;     //*1

    return ret;

}

// 受信テスト
int __fastcall TForm2::FifoExam_rcv( void )
{
String str;
FT_STATUS ftStatus;
DWORD writtenBytes;
DWORD EventDWord;
DWORD RxBytes;
DWORD RxBytes1;
DWORD TxBytes;
DWORD BytesReceived;
char *RxData;
String DiffTime;
long fDiffTIme;
long nn;
int ret;
    AddMemo("受信テスト");

    RxBytes = 10000000;
    RxData = new char[RxBytes];   // *1
    DWORD InTransferSize = 32768;//16384;
    ftStatus = FT_SetUSBParameters(handle, InTransferSize, 0);
    AddMemo("FT_SetUSBParameters(32768)");

    FT_Purge(handle, FT_PURGE_RX);
    AddMemo("FT_Purge");

	ret = -1;
    for(;;){
        //Application->ProcessMessages();
        ftStatus = FT_GetStatus(handle, &RxBytes1, &TxBytes, &EventDWord);

        if(ftStatus != FT_OK){
            AddMemo("FT_GetStatus ERROR");
            break;
        }else{
            if (RxBytes1 == 0) {
                continue;
            }
        }

        QueryPerformanceCounter(&gStartTime); //開始時間

        ftStatus = FT_Read(handle, RxData, RxBytes, &BytesReceived);

        if(ftStatus != FT_OK){
            AddMemo("FT_Read ERROR");
            break;
        }
        QueryPerformanceCounter(&gEndTime); //終了時間

        fDiffTIme = ((gEndTime.QuadPart - gStartTime.QuadPart)*1000 / gCpuFreq.QuadPart);
        DiffTime.sprintf("%d [mSec]", (DWORD)fDiffTIme);
        AddMemo( DiffTime ) ;

        nn = 1000*(RxBytes / (fDiffTIme+0.0000000001));
        String tmp;
        tmp.sprintf( "%d bytes---%6.3f [MBytes/sec] " ,RxBytes,  (float)nn/1000000.0 );
        AddMemo( tmp  ) ;

		ret = 0;
        //正常終了
        break;
    }
    delete []RxData;   // *1
    AddMemo("................");
    return ret;
}