xr21b1411 Exar Corporation, xr21b1411 Datasheet - Page 5

• Manufacturer Part Number: xr21b1411
• Description: Enhanced 1-ch Full-speed Usb Uart
• Manufacturer: Exar Corporation

REV. 1.1.0
The USB interface of the B1411 is compliant with the USB 2.0 Full-Speed Specifications.
The B1411 uses the following set of parameters:
Exar’s USB Vendor ID is 0x04E2. This is the default Vendor ID that is used for the B1411. This value can be
changed by programming the internal OTP via the USB link.
The default USB Product ID for the B1411 is 0x1411. This value can be changed by programming the internal
OTP via the USB link.
The B1411 device can be used with either a standard CDC-ACM driver or a custom driver. When the CDC-
ACM driver is used, the driver has no knowledge of the B1411 device registers. Because of this, the B1411
device is initialized to the following settings:
These default settings can be overridden by programming the OTP via the Address Value feature.
If a custom driver is used, the CUSTOM_DRIVER_ACTIVE bit should be immediately set to ’1’ by the driver.
Once the CUSTOM_DRIVER_ACTIVE bit is set, the custom driver can use standard CDC-ACM commands
without configuring the device to the default register settings used with the CDC-ACM driver. Any changes to
the register settings for the GPIOs and flow control will specifically need to be configured by the driver.
The UART can be configured via USB control transfers from the USB host. The UART transmitter and receiver
sections are described seperately below.
The transmitter consists of a 128-byte TX FIFO and a Transmit Shift Register (TSR). Once a bulk-out packet
has been received and the CRC has been validated, the data bytes in that packet are written into the TX FIFO.
Data from the TX FIFO is transferred to the TSR when the TSR is idle or has completed sending the previous
data byte. The TSR shifts the data out onto the TX output pin at the selected baud rate. The transmitter sends
1.0 FUNCTIONAL DESCRIPTIONS
1.1
1.2
1.3
1.1.1
1.1.2
1.3.1
1 Control Endpoint
1 Configuration is supported
2 interfaces for the UART channel
GPIO_DIRECTION
FLOW_CONTROL
GPIO_INT_MASK
Endpoint 0 as outlined in the USB specifications
Single interrupt endpoint
Bulk-in and bulk-out endpoints
GPIO_MODE
USB interface
USB Device Driver
UART
R
EGISTER
USB Vendor ID
USB Product ID
Transmitter
T
ABLE
1: B1411 R
V
0x001
0x001
0x008
0x030
ALUE
EGISTER
DTR configured as an output (in addition to RTS which is set by
RI, CD and DSR are interrupt sensitive, i.e. can cause a USB
D
EFAULTS WITH
5
interrupt to be generated
RTS / CTS flow control
Hardware flow control
CDC-ACM D
GPIO_MODE)
ENHANCED 1-CH FULL-SPEED USB UART
N
OTES
RIVER
XR21B1411