## Overview of FT240XQ-R The **FT240XQ-R** is a compact USB-to-parallel FIFO interface chip developed by FTDI Chip. It is part of the **FT-X series**, designed to bridge a USB 2.0 Full Speed interface with a standard 8-bit parallel FIFO bus. --- ### 1. Key Technical Specifications | Feature | Specification | | :--- | :--- | | **Interface** | USB 2.0 Full Speed (12Mbps) to 8-bit Parallel FIFO | | **Package** | 24-pin QFN (Lead-free) | | **FIFO Buffer** | 512 Byte Receive / 512 Byte Transmit | | **Operating Voltage** | 3.3V to 5.25V | | **Data Rate** | Up to 1 MB/s | | **Internal Clock** | Fully integrated (No external crystal required) | | **MTP Memory** | 2048 Bytes for storing device descriptors/CBUS | --- ### 2. Major Component Subsystems #### A. The USB Transceiver and Serial Interface Engine (SIE) This section handles the physical USB signaling (D+ and D-). The SIE manages the low-level USB protocol, including data integrity checks and handshake signals, removing the need for the user to write complex USB firmware. #### B. FIFO Control Logic The FT240X manages the flow of data between the USB buffer and the external 8-bit bus. It uses specific control signals: * **RXF#**: When low, indicates that there is data available in the FIFO to be read. * **TXE#**: When low, indicates that the FIFO is ready to accept data for transmission. * **RD# / WR#**: Used by the external MCU/FPGA to read from or write to the buffers. #### C. CBUS I/O Pins There are multi-function "CBUS" pins that can be configured for different tasks, such as: * Driving status LEDs (TX/RX activity). * Clock output (6MHz, 12MHz, or 24MHz) to drive an external MCU. * Battery Charger Detection (BCD) to identify if the device is plugged into a dedicated charging port. #### D. Internal Voltage Regulator The chip includes a **3.3V LDO regulator**. This allows the chip to operate from a 5V USB bus power supply while providing a regulated 3.3V output for internal logic and external low-power components. --- ### 3. Typical Pinout Functions (24-pin QFN) | Pin Type | Name | Description | | :--- | :--- | :--- | | **Power** | VCC / VCCIO | Main power and I/O voltage level supply. | | **USB** | USBDP / USBDM | USB Positive and Negative differential data signals. | | **Data** | D0 - D7 | 8-bit bidirectional FIFO data bus. | | **Control** | RD#, WR#, RXF#, TXE# | Handshaking and strobe signals for data transfer. | | **Config** | RESET# / CBUS | Device reset and configurable I/O functions. | --- ### 4. Use Cases * **Legacy Port Replacement:** Converting older parallel designs to USB. * **MCU-to-PC Communication:** Rapidly adding USB functionality to a microcontroller without a native USB peripheral. * **FPGA Interfacing:** Providing a simple 8-bit bus for FPGAs to stream data to a computer. ---