FT2232D datasheet(21/56 Pages) FTDI

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DS2232D Version 0.91

FT2232D Dual USB UART / FIFO I.C.

8.2 EEPROM Configuration

Figure 7 illustrates how to connect the FT2232D to the

93C46 (93C56 or 93C66) EEPROM. EECS (pin 48) is directly

connected to the chip select (CS) pin of the EEPROM. EESK

(pin 1) is directly connected to the clock (SK) pin of the

EEPROM. EEDATA (pin 2) is directly connected to the Data

In (Din) pin of the EEPROM. There is a potential condition

whereby both the Data Output (Dout) of the EEPROM can drive

out at the same time as the EEDATA pin of the FT2232D. To

prevent potential data clash in this situation, the Dout of the

EEPROM is connected to EEDATA of the FT2232D via a 2.2K

resistor.

Following a power-on reset or a USB reset, the FT2232D will

scan the EEPROM to find out (a) if an EEPROM is attached to

the Device and (b) if the data in the device is valid. If both of

these are the case, then the FT2232D will use the data in the

EEPROM, otherwise it will use its built-in default values and

configuration. The default port configuration of the FT2232D

puts both Channel A and Channel B into serial UART mode.

When a valid command is issued to the EEPROM from the

FT2232D, the EEPROM will acknowledge the command by

pulling its Dout pin low. In order to check for this condition,

it is necessary to pull Dout high using a 10K resistor. If the

command acknowledge doesn’t happen then EEDATA will be

pulled high by the 10K resistor during this part of the cycle

and the device will detect an invalid command or no EEPROM

present.

2.2K

VCC

EECS

EEDATA

FT2232C

EESK

DIN

DOUT

GND

VCC

EEPROM - 93C46 / 56 / 66

10K

VCC

Figure

EEPROM Configuration

There are two varieties of 93C46/56/66 EEPROM’s on the market – one is configured as being 16 bits wide, the other

is configured as being 8 bits wide. These are available from many sources such as Microchip, STMicro, ISSI etc. The

FT2232D requires EEPROM’s with a 16-bit wide configuration such as the Microchip 93LC46B device. The EEPROM

must be capable of reading data at a 1Mb clock rate at a supply voltage of 4.35V to 5.25V. Most available parts are

capable of this. Check the manufacturers data sheet to find out how to connect pins 6 and 7 of the EEPROM. Some

devices specify these as no-connect, others use them for selecting 8 / 16 bit mode or for test functions. Some other

parts have their pinout rotated by 90o so please select the required part and its options carefully.

It is possible to “share” the EEPROM between the FT2232D and another external device such as an MCU. However,

this can only be done when the FT2232D is in its reset condition as it tri-states its EEPROM interface at that time. A

typical configuration would use four bits of an MCU IO Port. One bit would be used to hold the FT2232D reset (using

RESET#) on power-up, the other three would connect to the EECS, EESK and EEDATA pins of the FT2232D in

order to read / write data to the EEPROM at this time. Once the MCU has read / written the EEPROM, it would take

RESET# high to allow the FT2232D to configure itself and enumerate over USB.

The external EEPROM can be programmed over USB using utility software provided by FTDI. The external EEPROM

is used to enable 245 FIFO, and Fast Opto-Isolated Serial interface modes on each channel.

FT2232D

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