UM10413
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© NXP B.V. 2011. All rights reserved.
User manual
Rev. 1 — 16 December 2011
87 of 268
NXP Semiconductors
UM10413
MPT612 User manual
14.3.9 UART0 Line status register (U0LSR - 0xE000 C014, read only)
The U0LSR is a read-only register that provides status information on the UART0 Tx and
Rx blocks.
Table 94:
UART0 Line status register (U0LSR - address 0xE000 C014, read only) bit description
Bit Symbol
Value Description
Reset value
0
Receiver Data
Ready
(RDR)
U0LSR0 set when U0RBR holds an unread character and is cleared when
UART0 RBR FIFO is empty
0
0
U0RBR is empty
1
U0RBR contains valid data
1
Overrun Error
(OE)
overrun error condition set when overrun occurs. An U0LSR read clears
U0LSR1. U0LSR1 is set when UART0 RSR has a new character assembled
and UART0 RBR FIFO is full. In this case, UART0 RBR FIFO is not
overwritten and character in UART0 RSR is lost.
0
0
overrun error status is inactive
1
overrun error status is active
2
Parity Error
(PE)
if parity bit of received character is wrong state, a parity error occurs. An
U0LSR read clears U0LSR[2]. Time of parity error detection is dependent on
U0FCR[0].
Remark:
Parity error is associated with character at top of UART0 RBR FIFO.
0
0
parity error status is inactive
1
parity error status is active
3
Framing Error
(FE)
if stop bit of received character is logic 0, a framing error occurs. An U0LSR
read clears U0LSR[3]. Time of framing error detection is dependent on
U0FCR0. Upon detection of a framing error, Rx attempts to resynchronize to
data and assumes bad stop bit is early start bit. However, it cannot be
assumed that next received byte is correct even if there is no framing error.
Remark:
Framing error is associated with character at top of UART0 RBR
FIFO.
0
0
framing error status is inactive
1
framing error status is active
4
Break Interrupt
(BI)
if RXD0 is held in spacing state (all 0s) for one full character transmission
(start, data, parity, stop), a break interrupt occurs. Once break condition is
detected, receiver goes idle until RXD0 goes to marking state (all 1s). A
U0LSR read clears this status bit. Time of break detection is dependent on
U0FCR[0].
Remark:
Break interrupt is associated with character at top of UART0 RBR
FIFO.
0
0
break interrupt status is inactive
1
break interrupt status is active
5
Transmitter
Holding Register
Empty
(THRE))
THRE is set immediately upon detection of an empty UART0 THR and is
cleared on a U0THR write
1
0
U0THR contains valid data
1
U0THR is empty
6
Transmitter
Empty
(TEMT)
TEMT is set when both U0THR and U0TSR are empty; TEMT is cleared when
either U0TSR or U0THR contain valid data
1
0
U0THR and/or the U0TSR contains valid data
1
U0THR and the U0TSR are empty