XR16M554 Datasheet, PDF (26/46 Pages) Exar Corporation – 1.62V TO 3.63V QUAD UART WITH 16-BYTE FIFO

XR16M554/554D
1.62V TO 3.63V QUAD UART WITH 16-BYTE FIFO
REV. 1.0.0
MCR[3]: INT Output Enable
Enable or disable INT outputs to become active or in three-state. This function is associated with the INTSEL
input, see below table for details. This bit is also used to control the OP2# signal during internal loopback
mode. INTSEL pin must be LOW during 68 mode.
• Logic 0 = INT (A-D) outputs disabled (three state) in the 16 mode (default). During internal loopback mode,
OP2# is HIGH.
• Logic 1 = INT (A-D) outputs enabled (active) in the 16 mode. During internal loopback mode, OP2# is LOW.
TABLE 12: INT OUTPUT MODES
INTSEL MCR
PIN BIT-3
INT A-D OUTPUTS IN 16 MODE
0
0
Three-State
0
1
Active
1
X
Active
MCR[4]: Internal Loopback Enable
• Logic 0 = Disable loopback mode (default).
• Logic 1 = Enable local loopback mode, see loopback section and Figure 11.
MCR[7:5]: Reserved (Default 0)
4.8 Line Status Register (LSR) - Read/Write
This register is writeable but it is not recommended. The LSR provides the status of data transfers between the
UART and the host. If IER bit-2 is enabled, LSR bit-1 will generate an interrupt immediately and LSR bits 2-4
will generate an interrupt when a character with an error is in the RHR.
LSR[0]: Receive Data Ready Indicator
• Logic 0 = No data in receive holding register or FIFO (default).
• Logic 1 = Data has been received and is saved in the receive holding register or FIFO.
LSR[1]: Receiver Overrun Flag
• Logic 0 = No overrun error (default).
• Logic 1 = Overrun error. A data overrun error condition occurred in the receive shift register. This happens
when additional data arrives while the FIFO is full. In this case the previous data in the receive shift register
is overwritten. Note that under this condition the data byte in the receive shift register is not transferred into
the FIFO, therefore the data in the FIFO is not corrupted by the error.
LSR[2]: Receive Data Parity Error Tag
• Logic 0 = No parity error (default).
• Logic 1 = Parity error. The receive character in RHR does not have correct parity information and is suspect.
This error is associated with the character available for reading in RHR.
LSR[3]: Receive Data Framing Error Tag
• Logic 0 = No framing error (default).
• Logic 1 = Framing error. The receive character did not have a valid stop bit(s). This error is associated with
the character available for reading in RHR.
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