2. Features and Enhancements of FT232R applicable to TTL-232R
2.1 FT232R Key Features
Page 3
The TTL-232R uses FTDI’s FT232RQ USB to serial IC device. This section summarises the key features and
enhancements of the FT232RQ which apply to the TTL-232R USB to serial TTL converter cable. For further details,
and a full features and enhancements description consult the FT232R datasheet, which is available from the
Lower Operating and Suspend Current -
The device operating supply current has been further reduced to 15mA,
and the suspend current has been reduced to around 70μA. This allows greater margin for peripheral devices
incorporating the TTL-232R to meet the USB suspend current limit of 500μA.
Low USB Bandwidth Consumption -
The operation of the USB interface to the FT232R IC, and thus the TTL-232R
has been designed to use as little as possible of the total USB bandwidth available from the USB host controller.
High Output Drive Option -
The UART interface I/O pins on the TTL-232R (RXD, TXD, RTS#, and CTS#) are
configured to use the FT232R’s high output drive option. This option makes the FT232R I.C.’s I/O pins drive out at
three times the standard signal drive level thus allowing multiple devices to be driven, or devices that require a greater
signal drive strength to be interfaced to the FT232R. This option is enabled in the internal EEPROM.
UART Pin Signal Inversion -
The sense of each of the eight UART signals can be individually inverted by setting
options in the internal EEPROM. Thus, CTS# (active low) can be changed to CTS (active high), or TXD can be
changed to TXD#.
FTDIChip-ID™ -
Each FT232R is assigned a unique number which is burnt into the device at manufacture. This ID
number cannot be reprogrammed by product manufacturers or end-users. This allows the possibility of using FT232R
based dongles 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
describing this feature is available separately from the
Improved EMI Performance -
The reduced operating current and improved on-chip VCC decoupling significantly
improves the ease of PCB design requirements for the FT232R in order to meet FCC, CE and other EMI related
specifications. The TTL-232R has passed FCC and CE testing.
Programmable Receive Buffer Timeout -
The receive buffer timeout is used to flush remaining data from the
receive buffer. This time defaults to 16ms, but is programmable over USB in 1ms increments from 1ms to 255ms, thus
allowing the device to be optimised for protocols that require fast response times from short data packets.
Baud Rates -
The TTL-232R supports all standard baud rates and non-standard baud rates from 300 Baud up to 3
Megabaud. Achievable non-standard baud rates are calculated as follows -
Baud Rate = 3000000 / (n +
x)
where n can be any integer between 2 and 16,384 ( = 2
14
) and
x
can be a sub-integer of the value 0, 0.125, 0.25,
0.375, 0.5, 0.625, 0.75, or 0.875. When n = 1,
x
= 0, i.e. baud rate divisors with values between 1 and 2 are not
possible.
This gives achievable baud rates in the range 183.1 baud to 3,000,000 baud. When a non-standard baud rate is
required simply pass the required baud rate value to the driver as normal, and the FTDI driver will calculate the
required divisor, and set the baud rate. See FTDI application note AN232B-05 for more details.
Extended Operating Temperature Range
- The TTL-232R is capable of operating over an extended temperature
range of -40º to +85º C thus allowing the device to be used in automotive and industrial applications.
TTL-232R USB to TTL Serial Converter Cable
Datasheet Version 1.0
© Future Technology Devices International Ltd. 2006
FTDI [ FUTURE TECHNOLOGY DEVICES INTERNATIONAL LTD. ]
