xr21v1412 Exar Corporation, xr21v1412 Datasheet - Page 8

• Manufacturer Part Number: xr21v1412
• Description: 2-ch Full-speed Usb Uart
• Manufacturer: Exar Corporation

XR21V1412
2-CH FULL-SPEED USB UART
In 9-bit data mode, two bytes of data must be written. The first byte that is loaded into the TX FIFO are the first
8 bits (data bits 7-0) of the 9-bit data. Bit-0 of the second byte that is loaded into the TX FIFO is bit-8 of the 9-
bit data. The data that is transmitted on the TX pin is as follows: start bit, 9-bit data, stop bit.
The receiver consists of a 384-byte RX FIFO and a Receive Shift Register (RSR). Data that is received in the
RSR via the RX pin is transferred into the RX FIFO along with any error tags such as Framing, Parity, Break
and Overrun errors. Data from the RX FIFO can be sent to the USB host by sending a bulk-in packet.
In character mode, up to 64 bytes of data can be sent at a time to the USB host.
In this mode, each 8-bit character and the 4 error bits associated with it can be transmitted to the USB host.
The 4 error bits will be in the second byte following the 8-bit character. In this mode, up to 32 character bytes
are sent per bulk-in packet.
In 9-bit data mode, two bytes of data are sent to the USB host for each byte 9-bit data that is received. The first
byte sent to the USB host is the first 8-bits of data. Bit-0 of the second byte is the bit-9 of the data.
Each UART has 6 GPIOs. By default, the GPIOs are general purpose I/Os. However, there are few modes
that can be enabled to add additional feature such as Auto RTS/CTS Flow control, Auto DTR/DSR Flow
Control or Transceiver Enable Control. See
GPIO5 and GPIO4 of the UART channel can be enabled as the RTS# and CTS# signals for Auto RTS/CTS
flow control when GPIO_MODE[2:0] = ’001’ and FLOW_CONTROL[2:0] = ’001’. Automatic RTS flow control is
used to prevent data overrun errors in local RX FIFO by de-asserting the RTS signal to the remote UART.
When there is room in the RX FIFO, the RTS pin will be re-asserted. Automatic CTS flow control is used to
1.4.1.1
1.4.2
1.4.2.1
1.4.2.2
1.4.2.3
1.4.3
1.4.4
Receiver
GPIO
Automatic RTS/CTS Hardware Flow Control
9-Bit Data Mode
Character Mode
Character + Status Mode
9-Bit Data Mode
Table
13.
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REV. 1.0.0