UM245R USB-Parallel FIFO Development Module Datasheet Version 1.02

© Future Technology Devices International Ltd. 2005

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2. FT232RL Features and Enhancements

2.1 Key Features

This section summarises the key features and enhancements of the FT245R IC device which is used in the UM245R

Module. For further details, consult the FT245R datasheet, which is available from the FTDI website.

Integrated Clock Circuit - Previous generations of FTDI’s USB to parallel FIFO interface devices required an external

crystal or ceramic resonator. The clock circuit has now been integrated onto the device meaning that no crystal or

ceramic resonator is required. However, if required, an external 12MHz crystal can be used as the clock source.

Integrated EEPROM - Previous generations of FTDI’s USB to parallel FIFO interface devices required an external

EEPROM if the device were to use USB Vendor ID (VID), Product ID (PID), serial number and product description

strings other than the default values in the device itself. This external EEPROM has now been integrated onto the

FT245R chip meaning that all designs have the option to change the product description strings. A user area of the

internal EEPROM is available for storing additional data. The internal EEPROM is programmable in circuit, over USB

without any additional voltage requirement.

Preprogrammed EEPROM - The FT245R is supplied with its internal EEPROM preprogrammed with a serial number

which is unique to each individual device. This, in most cases, will remove the need to program the device EEPROM.

Integrated USB Resistors - Previous generations of FTDI’s USB to parallel FIFO interface devices required two

external series resistors on the USBDP and USBDM lines, and a 1.5 kΩ pull up resistor on USBDP. These three

resistors have now been integrated onto the device.

Integrated AVCC Filtering - Previous generations of FTDI’s USB to parallel FIFO interface devices had a separate

AVCC pin - the supply to the internal PLL. This pin required an external R-C filter. The separate AVCC pin is now

connected internally to VCC, and the filter has now been integrated onto the chip.

Less External Components - Integration of the crystal, EEPROM, USB resistors, and AVCC filter will substantially

reduce the bill of materials cost for USB interface designs using the FT245R compared to its FT245BM predecessor.

Enhanced Asynchronous Bit Bang Mode with RD# and WR# Strobes - The FT245R supports FTDI’s BM chip bit

bang mode. In bit bang mode, the eight parallel FIFO data bus lines can be switched from the regular interface mode

to an 8-bit general purpose I/O port. Data packets can be sent to the device and they will be sequentially sent to the

interface at a rate controlled by an internal timer (equivalent to the baud rate prescaler). With the FT245R device this

mode has been enhanced so that the internal RD# and WR# strobes are now brought out of the device which can be

used to allow external logic to be clocked by accesses to the bit bang I/O bus. This option will be described more fully

in a separate application note

Synchronous Bit Bang Mode - Synchronous bit bang mode differs from asynchronous bit bang mode in that the

interface pins are only read when the device is written to. Thus making it easier for the controlling program to measure

the response to an output stimulus as the data returned is synchronous to the output data. The feature was previously

seen in FTDI’s FT2232C device. This option will be described more fully in a separate application note.

Lower Supply Voltage - Previous generations of the chip required 5V supply on the VCC pin. The FT245R will work

with a Vcc supply in the range 3.3V - 5V. Bus powered designs would still take their supply from the 5V on the USB

bus, but for self powered designs where only 3.3V is available, and there is no 5V supply, there is no longer any need

for an additional external regulator.

Integrated Level Converter on FIFO Interface and Control Signals - VCCIO pin supply can be from 1.8V to 5V.

Connecting the VCCIO pin to 1.8V, 2.8V, or 3.3V allows the device to directly interface to 1.8V, 2.8V or 3.3V and other

logic families without the need for external level converter I.C.s

5V / 3.3V / 2.8V / 1.8V Logic Interface - The FT245R provides true CMOS Drive Outputs and TTL level Inputs.

Integrated Power-On-Reset (POR) Circuit- The device incorporates an internal POR function. A RESET# pin is

available in order to allow external logic to reset the FT245R where required. However, for many applications the

RESET# pin can be left unconnected, or pulled up to VCCIO.