SC16IS740_750_760_6 © NXP B.V. 2008. All rights reserved.
Product data sheet Rev. 06 — 13 May 2008 26 of 62
NXP Semiconductors
SC16IS740/750/760
Single UART with I
2
C-bus/SPI interface, 64-byte FIFOs, IrDA SIR
8.5 Line Status Register (LSR)
Table 16 shows the Line Status Register bit settings.
When the LSR is read, LSR[4:2] reflect the error bits (BI, FE, PE) of the character at the
top of the RX FIFO (next character to be read). Therefore, errors in a character are
identified by reading the LSR and then reading the RHR.
LSR[7] is set when there is an error anywhere in the RX FIFO, and is cleared only when
there are no more errors remaining in the FIFO.
Table 16. Line Status Register bits description
Bit Symbol Description
7 LSR[7] FIFO data error.
logic 0 = no error (normal default condition)
logic 1 = at least one parity error, framing error, or break indication is in the
receiver FIFO. This bit is cleared when no more errors are present in the
FIFO.
6 LSR[6] THR and TSR empty. This bit is the Transmit Empty indicator.
logic 0 = transmitter hold and shift registers are not empty
logic 1 = transmitter hold and shift registers are empty
5 LSR[5] THR empty. This bit is the Transmit Holding Register Empty indicator.
logic 0 = transmit hold register is not empty
logic 1 = transmit hold register is empty. The host can now load up to
64 characters of data into the THR if the TX FIFO is enabled.
4 LSR[4] break interrupt
logic 0 = no break condition (normal default condition)
logic 1 = a break condition occurred and associated character is 0x00, that
is, RX was LOW for one character time frame
3 LSR[3] framing error
logic0=noframing error in data being read from RX FIFO (normal default
condition).
logic 1 = framing error occurred in data being read from RX FIFO, that is,
received data did not have a valid stop bit
2 LSR[2] parity error.
logic 0 = no parity error (normal default condition)
logic 1 = parity error in data being read from RX FIFO
1 LSR[1] overrun error
logic 0 = no overrun error (normal default condition)
logic 1 = overrun error has occurred
0 LSR[0] data in receiver
logic 0 = no data in receive FIFO (normal default condition)
logic 1 = at least one character in the RX FIFO
