XR16M752 EXAR [Exar Corporation], XR16M752 Datasheet - Page 25

• Manufacturer Part Number: XR16M752
• Description: HIGH PERFORMANCE DUART WITH 64-BYTE FIFO
• Manufacturer: EXAR [Exar Corporation]

REV. 1.0.2
When FCR BIT-0 equals a logic 1 for FIFO enable; resetting IER bits 0-3 enables the XR16M752 in the FIFO
polled mode of operation. Since the receiver and transmitter have separate bits in the LSR either or both can
be used in the polled mode by selecting respective transmit or receive control bit(s).
A. LSR BIT-0 indicates there is data in RHR or RX FIFO.
B. LSR BIT-1 indicates an overrun error has occurred and that data in the FIFO may not be valid.
C. LSR BIT 2-4 provides the type of receive data errors encountered for the data byte in RHR, if any.
D. LSR BIT-5 indicates THR is empty.
E. LSR BIT-6 indicates when both the transmit FIFO and TSR are empty.
F. LSR BIT-7 indicates a data error in at least one character in the RX FIFO.
IER[0]: RHR Interrupt Enable
The receive data ready interrupt will be issued when RHR has a data character in the non-FIFO mode or when
the receive FIFO has reached the programmed trigger level in the FIFO mode.
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IER[1]: THR Interrupt Enable
This bit enables the Transmit Ready interrupt which is issued whenever the THR becomes empty in the non-
FIFO mode or when spaces in the FIFO is above the programmed trigger level in the FIFO mode. If the THR is
empty when this bit is enabled, an interrupt will be generated.
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IER[2]: Receive Line Status Interrupt Enable
If any of the LSR register bits 1, 2, 3, 4 or 7 is a logic 1, it will generate an interrupt to inform the host controller
about the error status of the current data byte in FIFO. LSR bit-1 generates an interrupt immediately when the
character has been received. LSR bit-7 is set if any character in the RX FIFO has a parity or framing error, or is
a break character. LSR[4:2] always show the error status for the received character available for reading from
the RX FIFO. If IER[2] = 1, an LSR interrupt will be generated as long as LSR[7] = 1, ie. the RX FIFO contains
at lease one character with an error.
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IER[3]: Modem Status Interrupt Enable
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IER[4]: Sleep Mode Enable (requires EFR bit-4 = 1)
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IER[5]: Xoff Interrupt Enable (requires EFR bit-4=1)
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4.3.2
Logic 0 = Disable the receive data ready interrupt (default).
Logic 1 = Enable the receiver data ready interrupt.
Logic 0 = Disable Transmit Ready interrupt (default).
Logic 1 = Enable Transmit Ready interrupt.
Logic 0 = Disable the receiver line status interrupt (default).
Logic 1 = Enable the receiver line status interrupt.
Logic 0 = Disable the modem status register interrupt (default).
Logic 1 = Enable the modem status register interrupt.
Logic 0 = Disable Sleep Mode (default).
Logic 1 = Enable Sleep Mode. See Sleep Mode section for further details.
Logic 0 = Disable the software flow control, receive Xoff interrupt (default).
Logic 1 = Enable the receive Xoff interrupt. See Software Flow Control section for details.
IER versus Receive/Transmit FIFO Polled Mode Operation
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HIGH PERFORMANCE DUART WITH 64-BYTE FIFO
XR16M752/XR68M752