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Dual-channel UART supports 8Mbps data rates

Posted: 18 Apr 2007     Print Version  Bookmark and Share

Keywords:dual-channel UART  RS-485 transceiver  industrial networking 

Exar released a dual-channel, 8bit UART with integrated RS-485 transceiver device family that can support up to 8Mbps data rates. The XR19L402/400 series targets industrial peripheral applications including point-of-sale, factory automation and industrial networking systems.

The series offers different packaging and modem interface options. Both devices can operate in four different modes: active, partial sleep, full sleep and power-save. Each mode can be invoked via hardware or software.

Upon power-up, the device is in the active mode where the UART and RS-485 transceiver function normally. In the partial-sleep mode, the internal crystal oscillator of the UART, or the charge pump of the RS-485 transceiver, is turned off. In full-sleep mode, both the crystal oscillator and the charge pump are turned off. While the UART is in the sleep mode, the power-save mode isolates the core logic from the control signals (chip select, read/write strobes, address and data bus lines) to minimise the power consumption. The RS-485 receivers remain active in each of these four modes.

The devices operate from a single 3-5.5V supply with data rates up to 8Mbps, while meeting all EIA/TIA-485 specifications. The configuration register set is "16550 UART" compatible for control, status and data transfer. The devices also have 64bytes of transmit and receive FIFOs, automatic RTS/CTS hardware flow control, automatic Xon/Xoff and special character software flow control, transmit and receive FIFO trigger levels, and a programmable fractional baud rate generator with a prescaler of divide by 1 or 4. Moreover, the devices include an ACP pin that allows the user to shut down the charge pump for the RS-485 drivers. In the UART portion, the Power-Save feature isolates the data bus interface to further reduce power consumption during sleep mode.

Samples of the product series are available. Pricing starts at around Rs.88 ($2) each in 1,000-piece quantities.

- Emily Gleason

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