The **FT221XS-R** is a compact, high-performance USB-to-8-bit Wide FIFO interface chip developed by **FTDI Chip**. It belongs to the FT-X series, designed to reduce component count and PCB footprint by integrating many external functions onto the chip. --- ### ## 1. Key Technical Specifications Below is a breakdown of the primary electrical and physical characteristics of the FT221XS-R. | Parameter | Specification | |:---|:---| | **Interface** | USB 2.0 Full Speed to 8-bit Wide FIFO | | **Data Rate** | Up to 11 MB/s (FIFO) | | **Operating Voltage** | +3.3V to +5.25V | | **I/O Voltage Support** | +1.8V to +3.3V | | **Package Type** | SSOP-20 (Shrink Small Outline Package) | | **Internal Memory** | 512 bytes MTP (Multi-Time Programmable) | | **Clock Source** | Integrated (No external crystal required) | --- ### ## 2. Core Functional Blocks The FT221XS-R integrates several hardware blocks that typically require external components in older designs: 1. **Integrated Clock Circuit:** Unlike older USB chips, it does not require an external crystal, saving board space and cost. 2. **USB Transceiver:** Includes the physical layer (PHY) for USB 2.0 Full Speed communication. 3. **512-Byte MTP Memory:** Used for storing the USB VID, PID, serial number, and product description strings. This can be programmed in-circuit over USB. 4. **Voltage Regulator:** An internal 3.3V LDO regulator allows the chip to be powered directly from the USB 5V VBUS while providing power to the internal logic. 5. **Configurable CBUS Pins:** Includes 2 multi-function I/O pins that can be configured for tasks like driving status LEDs or sending sleep/wake signals. --- ### ## 3. Interface and Connectivity The FT221XS-R uses a **synchronous or asynchronous FIFO** protocol to communicate with an external MCU or FPGA. * **FIFO Pins:** `D0` through `D7` (8-bit data bus). * **Control Signals:** * `RXF#`: Receiver Full (Data available to be read). * `TXE#`: Transmitter Empty (Ready to accept data). * `RD#`: Read trigger. * `WR#`: Write trigger. --- ### ## 4. Application Example (Circuit Concept) The following represents a simplified connection logic for the FT221XS-R: ```text [ USB Connector ] <-----> [ FT221XS-R ] <-----> [ Microcontroller/FPGA ] (VBUS/D+/D-) (FIFO Bus) (8-bit Parallel I/O) (CBUS Pins) (Status/Interrupts) ``` **Common use cases include:** * Upgrading legacy parallel designs to USB. * High-speed data acquisition systems. * MCU/FPGA to PC communication where high throughput is required. * USB Industrial Control interfaces. ---