XR21V1414 Просмотр технического описания (PDF) - Exar Corporation

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XR21V1414

4-CH FULL-SPEED USB UART

Exar Corporation 

XR21V1414

REV. 1.1.0

4-CH FULL-SPEED USB UART

1.0 FUNCTIONAL DESCRIPTIONS

1.1 USB interface

The USB interface of the V1414 is compliant with the USB 2.0 Full-Speed Specifications. The USB

configuration model presented by the V1414 to the device driver is compatible to the Abstract Control Model of

the USB Communication Device Class (CDC-ACM). The V1414 uses the following set of parameters:

• 1 Control Endpoint

s Endpoint 0 as outlined in the USB specifications

• 1 Configuration is supported

• 2 interfaces per UART channel

s Each UART channel has a single interrupt endpoint

s Each UART channel have bulk-in and bulk-out endpoints

1.1.1 USB Vendor ID

Exar’s USB Vendor ID is 0x04E2. This is the default Vendor ID that is used for the V1414 unless a valid

EEPROM is present on the I2C interface signals. If a valid EEPROM is present, the Vendor ID from the

EEPROM will be used.

1.1.2 USB Product ID

The default USB Product ID for the V1414 is 0x1414. If a valid EEPROM is present, the Product ID from the

EEPROM will be used.

1.2 USB Device Driver

The V1414 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 V1414 device registers. Because of this, the V1414

device is initialized to the following settings:

TABLE 1: V1414 REGISTER DEFAULTS WITH CDC-ACM DRIVER

REGISTER

VALUE

NOTES

FLOW_CONTROL

0x01

Hardware flow control

GPIO_MODE

0x01

RTS / CTS flow control

GPIO_DIRECTION

0x08

DTR configured as an output (in addition to RTS which is set by

GPIO_MODE)

GPIO_INT_MASK

0x30

CD and DSR are interrupt sensitive, i.e. can cause a USB inter-

rupt to be generated

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