Honored Contributor
Honored ContributorAs a short update, I verified that a FT2232 can be used with Arrow-USB-Blaster driver and configuration without additional hardware. It uses the same JTAG pin assignment as the FTDI JTAG tool (TCK = AD0, TDI = AD1, TDO = AD2, TMS = AD3).
To drive usual pull-up and pull-down resistors, the "High Current I/O's" option must be enabled in the PORT_A configuration. (It can be set in FTDI FT_PROG tool when writing the EEPROM configuration). This makes me think, that BeMicro uses additional buffers or pull-up and pull-down resistors of higher resistance. Also, the FT2232 I/O operation isn't specified for VCCIO below 3 V. I didn't check, if it possibly works at 2.5V as well. Furthermore, TCK is known to be susceptible to crosstalk from other fast digital signals, an unsuitable driver impedance can also cause ringing TCK edges and JTAG failure. So a TCK driver may be recommended in some applications. The Arrow USB Blaster uses a TCK of 6 MHz, which is the maximum clock frequency in FTDI MPSSE mode. The overall operation is slower than a standard USB Blaster. I got about 50 - 100 % longer programming times in my test. This particularly matters in time consuming flash programming actions. All tests have been performed with Quartus Programmer. I wonder, if the performance differences are caused by ineffective programming or real hardware and FTDI driver properties. But I think, it's an interesting tool anyway.
