FT232BQ datasheet(4/25 Pages) FTDI

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DS232B Version 1.8

Page 4 of 25

FT232BM USB UART ( USB - Serial) I.C.

•

Less External Support Components

As well as eliminating the RCCLK RC network, and

for most applications the need for an external reset

circuit, we have also eliminated the requirement for

a 100K pull-up on EECS to select 6MHz operation.

When the FT232BM is being used without the

conﬁguration EEPROM, EECS, EESK and EEDATA

can now be left n/c. For circuits requiring a long

reset time (where the device is reset externally

using a reset generator I.C., or reset is controlled

by the IO port of a MCU, FPGA or ASIC device) an

external transistor circuit is no longer required as the

1.5k pull-up resistor on USBDP can be wired to the

RSTOUT# pin instead of to 3.3V. Note : RSTOUT#

drives out at 3.3V level, not at 5V VCC level. This is

the preferred conﬁguration for new designs.

•

Extended EEPROM Support

The previous generation of devices only supported

EEPROM of type 93C46 (64 x 16 bit). The new

devices will also work with EEPROM type 93C56

(128 x 16 bit) and 93C66 (256 x 16 bit). The extra

space is not used by the device, however it is

available for use by other external MCU / logic whilst

the FT232BM is being held in reset.

•

USB 2.0 (full speed option)

A new EEPROM based option allows the FT232BM

to return a USB 2.0 device descriptor as opposed to

USB 1.1. Note : The device would be a USB 2.0 Full

Speed device (12Mb/s) as opposed to a USB 2.0

High Speed device (480Mb/s).

•

Multiple Device Support without EEPROM

When no EEPROM (or a blank or invalid

EEPROM) is attached to the device, the FT232BM

no longer gives a serial number as part of its

USB descriptor. This allows multiple devices to

be simultaneously connected to the same PC.

However, we still highly recommend that EEPROM

is used, as without serial numbers a device can

only be identiﬁed by which hub port in the USB tree

it is connected to which can change if the end user

re-plugs the device into a different port.

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