Copyright © 2009 Future Technology Devices International Limited
11
Document Reference No.: FT_000151
DS_US232R-10(R-100)
USB TO RS232 ADAPTER CABLE Data
Sheet
Version 1.0
Clearance No.: #
99
2.1.6
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
FTDI
website
.
2.1.7
Improved EMI Performance
The reduced operating current and improved on-chip VCC decoupling significantly
improves the ease of PCB design requirements in order to meet FCC, CE and other EMI
related specifications.
2.1.8
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.
2.1.9
Baud Rates
The FT232R supports all standard baud rates and non-standard baud rates from 300
Baud up to 3 Mbaud. 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
The US232R cable is limited to a maximum of 1 Mbaud because of the line driver within
the circuit.
