XR21B1422IL40-0A Datasheet, PDF (18/60 Pages) Exar Corporation – Enhanced 2-Ch Full-Speed USB UART

XR21B1422
Note that USE_SUSPEND does not affect the UART RX and TX pins. During suspend state, RX and TX will always idle to a
logic ’1’ state.
The SUSPEND_STATE field will set or clear the GPIO pins and the SUSPEND_MODE field will configure GPIO outputs as
either open drain or push-pull outputs. SUSPEND_STATE and SUSPEND_MODE may be configured through registers or
OTP. As opposed to OTP configuration, register configurations are not retained if the power is lost or the bus is reset.
TXT and RXT Pins
The Transmit toggle and Receive toggle pins "toggle" at a rate of approximately 10 Hz whenever the UART transmit and
receive pins (respectively) are active.
OTP
The OTP is an on-chip non-volatile memory, that is incrementally one-time programmable via the USB interface. Some bits
are pre-programmed at the factory and caution must be taken not to program any locations except those user defined
addresses given in this data sheet. Once a specific portion of the OTP is programmed, the PROG bit for that section of the
OTP must be set and further changes to that section will not be allowed.
© 2014 Exar Corporation
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Rev 1A