Document Reference No.: FT_000117
USB TO RS485 SERIAL CONVERTER CABLE Datasheet
Version 1.4
Clearance No.: FTDI #75
4 Features of FT232R applicable to USB-RS485 Cable
The USB-RS485 cable uses FTDI‟s FT232RQ USB to serial UART IC device. This section summarises the
key features of the FT232RQ which apply to the USB-RS485 USB to serial RS485 converter cables. For
further details, and a full features and enhancements description consult the FT232R datasheet. This is
available from www.ftdichip.com.
Internal EEPROM. The internal EEPROM in each cable is used to store USB Vendor ID (VID), Product ID
(PID), device serial number, product description string and various other USB configuration descriptors.
Each cable is supplied with the internal EEPROM pre-programmed as described in Appendix A –Cable
EEPROM Configuration. The internal EEPROM descriptors can be programmed in circuit, over USB
without any additional voltage requirement. It can be programmed using the FTDI utility software called
MPROG, which can be downloaded from FTDI Utilities on the FTDI website (www.ftdichip.com).
Additionally, there is a user area of the internal EEPROM available to system designers to allow storing of
data (note that this is not modified by MPROG).
Lower Operating and Suspend Current. The FT232R has a low 15mA operating supply current and a
very low USB suspend current of approximately 70μA. (Note that during suspend mode, the current
drawn by any customised cable application which uses the USB supply, should not exceed 2.5mA to
remain USB compliant)
Low USB Bandwidth Consumption. The USB interface of the FT232R, and therefore the USB-RS485
cables has been designed to use as little as possible of the total USB bandwidth available from the USB
host controller.
FTDIChip-ID™. The FT232R includes the new FTDIChip-ID™ security dongle feature. This FTDIChip-ID™
feature allows a unique number to be burnt into each cable during manufacture. This number cannot be
reprogrammed. This number is only readable over USB can be used to form the basis of a security dongle
which can be used to protect any customer application software being copied. This allows the possibility
of using the USB-RS485 cables as a dongle for software licensing. Further to this, a renewable license
scheme can be implemented based on the FTDIChip-ID™ number when encrypted with other information.
This encrypted number can be stored in the user area of the FT232R internal EEPROM, and can be
decrypted, then compared with the protected FTDIChip-ID™ to verify that a license is valid. Web based
applications can be used to maintain product licensing this way. An application note, AN232R-02,
available from FTDI website (www.ftdichip.com) describes this feature.
Improved EMI Performance. The USB-RS485 cables are FCC and CE certified.
Extended Operating Temperature Range - The USB-RS485 cables are capable of operating over an
extended temperature range of -40º to +85º C thus allowing them to be used in automotive or industrial
applications.
Copyright © 2010 Future Technology Devices International Limited
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