XR21B1421 Datasheet, PDF (22/50 Pages) Exar Corporation – Enhanced 1-Ch Full-Speed

XR21B1421
HID Report Descriptions
All of the functionality of the XR21B1421 device is controlled via HID reports. Some of these reports will program the on-
chip OTP memory. All of the HID reports in the OTP customization section (reports 0x47 and 0x60 through 0x67) will per-
manently program the on-chip OTP. All other HID reports do not program the OTP. The SET_GPIO_CONFIG (report 0x49)
dynamically configures the GPIO pins, but does not program the OTP as does the SET_PIN_CONFIG report.
SET_TRANSMIT_DATA
Transfer Type: Interrupt Out
Transfer Size: 2 - 64 bytes
The SET_TRANSMIT_DATA report transmits up to 63 bytes of data to the UART per transfer.
Field
Report ID
Data
Offset
0
Size
1
1
1-63
Value
0x01 - 0x3F
Description
Indicates the size of the data transfer to be sent to the device from 1 (0x01) to 63
(0x3F) bytes excluding the report ID itself.
Data from USB host to UART
GET_RECEIVE_DATA
Transfer Type: Interrupt In
Transfer Size: 2 - 64 bytes
The GET_RECEIVE_DATA report receives up to 63 bytes of data from the UART per transfer. This report is returned when
the USB host polls the Interrupt-In endpoint at 1 ms intervals.
Field
Report ID
Data
Offset
0
Size
1
1
1-63
Value
0x01 - 0x3F
Description
Indicates the size of the data transfer to be sent to the device from 1 (0x01) to 63
(0x3F) bytes excluding the report ID itself.
Data from USB host to UART
SET_DEVICE_RESET
Transfer Type: Control Out
Transfer Size: 2 bytes
The SET_DEVICE_RESET report performs a software reset of the XR21B1421 device that resets the USB interface and
clears the UART RX and TX FIFOs, but does not change any UART configuration settings or change any pin configurations.
Any changes to on-chip OTP will not be reflected following the software reset. During software reset, the internal pull-up on
the USBD+ pin will be disabled to signal the USB host that a detach event has occurred. Following reset, the pull-up resistor
will be enabled to signal an attach event to the USB host.
Field
Report ID
Value
Offset
0
1
Size
1
1
Value
0x40
Force device hardware reset
Set of any value forces reset
Description
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