Document No.: FT_000061
FT2232H DUAL HIGH SPEED USB TO MULTIPURPOSE UART/FIFO IC
Version 2.21
Clearance No.: FTDI#77
FT2232H Mode Selection
The 2 channels of the FT2232H reset to 2 asynchronous serial interfaces.
Following a reset the required mode of each channel is determined by the contents of the EEPROM
(programmed using MPROG V3.4a or later).
The EEPROM contents determine if the 2 channels have been configured as FT232 asynchronous serial
interface, FT245 FIFO interface, CPU-style FIFO interface or Fast Serial Interface.
Following a reset, the EEPROM is read to determine which mode is configured. After device enumeration,
an FT_SetBitMode command (refer to D2XX_Programmers_Guide) can be sent to the USB driver to
switch the selected interface into the required mode – asynchronous bit-bang, synchronous bit-bang or
MPSSE.
When in FT245 FIFO mode, the FT_SetBitMode command can be used to select either Synchronous
FIFO (FT_SetBitMode = 0x40) or Asynchronous FIFO mode. (Note that Asynchronous FIFO mode must
be selected on both channels before selecting the Synchronous FIFO mode. This means that an EEPROM
is needed to initially configure Asynchronous FIFO mode before software configures the Synchronous
FIFO mode).
When Synchronous FIFO mode selected, channel A uses all the memory resources of channel B. As such
channel B is then not available. In this case the state of the channel B pins is determined when the
configuration is switched to Asynchronous FIFO mode. If channel B had not been used for any data
transfer before configuration of Asynchronous FIFO mode, then the channel B pins will remain in their
default mode (D7:0=tri-stated but pulled high trough 75K resistor, TXE# =low, RXF# =high. RD# and
WR# are inputs and should be pulled high). An MPSSE command, set_data_bits can be used to
configure the channel B pins as inputs before configuring channel A as Synchronous FIFO. This avoids the
channel B pins driving against any interfaces (such as SPI) which may have been configured previous to
any switching of channel A to Synchronous FIFO mode. Refer to
http://www.ftdichip.com/Documents/AppNotes/AN2232C-01_MPSSE_Cmnd.pdf for the set_data_bits
command and further information on the MPSSE used in MCU Host BUS Emulation mode.
The MPSSE can be configured directly using the D2XX commands. The D2XX_Programmers_Guide is
available from the FTDI website at
http://www.ftdichip.com/Documents/ProgramGuides/D2XX_Programmer‟s_Guide(FT_000071).pdf
The application note AN_108 – “Command Processor For MPSSE and MCU Host Bus Emulation
Modes” gives further explanation and examples for the MPSSE.
4.12.1
Do I need an EEPROM?
The following table Table 4.11summarises what modes are configurable using the EEPROM or the
application software.
ASYNC
Serial
UART
ASYNC
245
FIFO
SYNC
245
FIFO
ASYN
C Bit-
bang
SYNC
Bit-
bang
MPSSE
Fast
Serial
interface
CPU-
Style Emulation
FIFO
Host Bus
EEPROM
configured
YES
YES
YES
YES
YES
YES
Application
Software
YES
YES
YES
YES
configured
Table 4.11 Configuration Using EEPROM and Application Software
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46
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