XR16V794 Datasheet, PDF (29/53 Pages) Exar Corporation – HIGH PERFORMANCE 2.25V TO 3.6V QUAD UART WITH FRACTIONAL

XR16V794
REV. 1.0.0
HIGH PERFORMANCE 2.25V TO 3.6V QUAD UART WITH FRACTIONAL BAUD RATE
IER[7]: CTS# Input Interrupt Enable (requires EFR bit-4=1)
• Logic 0 = Disable the CTS# interrupt (default).
• Logic 1 = Enable the CTS# interrupt. The UART issues an interrupt when CTS# pin makes a transition from
LOW to HIGH.
IER[6]: RTS# Output Interrupt Enable (requires EFR bit-4=1)
• Logic 0 = Disable the RTS# interrupt (default).
• Logic 1 = Enable the RTS# interrupt. The UART issues an interrupt when RTS# pin makes a transition from
LOW to HIGH.
IER[5]: Xoff Interrupt Enable (requires EFR bit-4=1)
• Logic 0 = Disable the software flow control, receive Xoff interrupt (default).
• Logic 1 = Enable the software flow control, receive Xoff interrupt. See Software Flow Control section for
details.
IER[4]: Reserved.
IER[3]: Modem Status Interrupt Enable
The Modem Status Register interrupt is issued whenever any of the delta bits of the MSR register (bits 3:0) is
set.
• Logic 0 = Disable the modem status register interrupt (default).
• Logic 1 = Enable the modem status register interrupt.
IER[2]: Receive Line Status Interrupt Enable
An Overrun error, Framing error, Parity error or detection of a Break character will result in an LSR interrupt.
The 794 will issue an LSR interrupt immediately after receiving a character with an error. It will again re-issue
the interrupt (if the first one has been cleared by reading the LSR register) when the character with the error is
on the top of the FIFO, meaning the next one to be read out of the FIFO.
For example, let’s consider an incoming data stream of 0x55, 0xAA, etc and that the character 0xAA has a
Parity error associated with it. Let’s assume that the character 0x55 has not been read out of the FIFO yet. The
794 will issue an interrupt as soon as the stop bit of the character 0xAA is received. The LSR register will have
only the FIFO error bit (bit-7) set and none of the other error bits (Bits 1,2,3 and 4) will be set, since the byte on
the top of the FIFO is 0x55 which does not have any errors associated with it. When this byte has been read
out, the 794 will issue another LSR interrupt and this time the LSR register will show the Parity bit (bit-2) set.
• Logic 0 = Disable the receiver line status interrupt (default).
• Logic 1 = Enable the receiver line status interrupt.
IER[1]: TX Ready Interrupt Enable
In non-FIFO mode, a TX interrupt is issued whenever the THR is empty. In the FIFO mode, an interrupt is
issued twice: once when the number of bytes in the TX FIFO falls below the programmed trigger level and
again when the TX FIFO becomes empty. When autoRS485 mode is enabled (FCTR bit-5 = 1), the second
interrupt is delayed until the transmitter (both the TX FIFO and the TX Shift Register) is empty.
• Logic 0 = Disable Transmit Ready Interrupt (default).
• Logic 1 = Enable Transmit Ready Interrupt.
IER[0]: RX 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.
• Logic 0 = Disable the receive data ready interrupt (default).
• Logic 1 = Enable the receiver data ready interrupt.
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