Actually I got how to read messages. I need to send to my FT device first byte 0x00, and then I get readed data.
 But how to write it? What D2xxs' FT_Write() does? If it writes data in buffer, then how to send it to my other device?
 I try to write to FT220X both FT1248 commands Read(0x00) and Write(0x01), but only one happens - I read data, but nothing writes. I checked MIOSI line and there is only my second devices' data, no FT220Xs' device answers.
 So, the question is in how FT_Write() func works and how to write data via FT220X conv from PC?

 I tried to define RxBuffer differently: integer, char, DWORD just for experiment. That doesn't change nothing

 As I checked, there must be at least one 4 (or 5, that's another question, why I get 4 bytes instead 5, when timings are Ok) bytes package {0x9E, 0x00, 0x00, 0x00, 0x03}.

 Another question. There is MIOSIs in FT1248 controller. The 0s' one is only for OUTPUT or for both of them?

Recently I tried to write program on C++, guided by your instructions on official cite. So, after completing writing I got on RxBytesBuffer strange data package. I get, for example, 0x00AFF738 and this bytes always change in ever iteration of using program.

Also I notice that this values have difference in 12. If I printf() them in %lu, I get RxBytes: 0x6421720, TxBytes: 0x6421732 and RxBuffer: 0x6421444. Is this kinda encrypting? And if this packages always change and they are encrypted, how I can uncrypt them?

In my device this chip in Slave mode. I need get 5 bytes, that contains answers from my SPI-Master device. And after getting command I need to write an answer to Master and continue communicate with it at same time with 485 port (but with communicating with 2 devices I have no problem).