The **XR19L400IL40** is a high-performance single-channel Universal Asynchronous Receiver and Transmitter (**UART**) designed by MaxLinear (formerly Exar). It is primarily used to facilitate serial communication between a microprocessor and external peripherals. --- ### ## Technical Specifications The following table highlights the core electrical and operational parameters of the XR19L400IL40. | Parameter | Specification | | :--- | :--- | | **Interface** | Intel or Motorola Bus Interface | | **Supply Voltage (VCC)** | 2.25V to 5.5V | | **Data Rate** | Up to 6.25 Mbps at 5V | | **FIFO Depth** | 16-byte Transmit and Receive | | **Package** | 40-pin QFN (6x6 mm) | | **Operating Temperature** | -40°C to +85°C (Industrial) | | **I/O Tolerance** | 5V Tolerant Inputs | --- ### ## Key Features The device is engineered for efficiency and low power consumption in embedded systems. * **FIFO Architecture:** It features a 16-byte FIFO (First-In, First-Out) buffer to reduce CPU overhead by allowing the UART to store data before the processor needs to intervene. * **Fractional Baud Rate Generator:** Provides high precision in setting baud rates, allowing it to work with a wide range of clock frequencies. * **Auto Hardware/Software Flow Control:** Supports RTS/CTS (hardware) and Xon/Xoff (software) flow control to prevent data loss during high-speed transfers. * **Sleep Mode:** Includes a power-saving mode that draws very little current when the device is idle, making it ideal for battery-operated devices. * **Modem Control Signals:** Provides a full set of modem control signals (CTS#, RTS#, DSR#, DTR#, CD#, RI#). --- ### ## Pinout Functional Groups The 40-pin QFN package organizes pins into several functional categories: 1. **Host Interface:** Data bus (D0-D7), Address lines (A0-A2), and control signals (CS#, IOR#, IOW#). 2. **UART Channel:** TX (Transmit) and RX (Receive) pins for the serial side. 3. **Modem Control:** Standard RS-232 control signals for handshaking. 4. **Clock/Reset:** XTAL1/XTAL2 for crystal input and a RESET pin to initialize the internal registers. --- ### ## Application Circuit Example To interface the XR19L400 with a microcontroller, a basic connection logic is required: ```c // Example: Pseudo-code for initializing the XR19L400 Baud Rate void UART_Init(uint16_t baud_divisor) { write_reg(LCR, 0x80); // Enable Divisor Latch (DLAB) write_reg(DLL, baud_divisor & 0xFF); // Set Low Byte write_reg(DLM, (baud_divisor >> 8) & 0xFF); // Set High Byte write_reg(LCR, 0x03); // Disable DLAB, Set 8N1 format } ``` ---