Intel PXA255 - Manual (Page 591)

Intel® PXA255 Processor Developer’s Manual 17-19
Hardware UART
17.5.11 Line Status Register (LSR)
The LSR, shown in Table 17-15 , provides data transfer status information to the processor.
In non-FIFO mode, LSR[4:2] show the parity error, framing error, break interrupt, and show the
error status of the character that has just been received.
In FIFO mode, LSR[4:2] show the status bits of the character that is currently at the front of the
FIFO.
LSR[4:1] produce a receiver line status interrupt when the corresponding conditions are detected
and the interrupt is enabled. In FIFO mode, the receiver line status interrupt only occurs when the
erroneous character reaches the front of the FIFO. If the erroneous character is not at the front of
the FIFO, a line status interrupt is generated after the other characters are read and the erroneous
character becomes the character at the front of the FIFO.
The LSR must be read before the erroneous character is read. LSR[4:1] bits are set until software
reads the LSR.
See Section 17.4.2.3 for details on using the DMA to receive data.
This is a read-only register. Ignore reads from reserved bits.
4 EPS
EVEN PARITY SELECT
Even parity select bit. If PEN = 0, EPS is ignored.
0 = Sends or checks for odd parity
1 = Sends or checks for even parity
3 PEN
PARITY ENABLE
Enables a parity bit to be generated on transmission or checked on reception.
0 = No parity
1 = Parity
2 STB
STOP BITS
Specifies the number of stop bits transmitted and received in each character. When
receiving, the receiver only checks the first stop bit.
0 = 1 Stop bit
1 = 2 Stop bits, except for 5-bit character then 1-1/2 bits
1:0 WLS[1:0]
WORD LENGTH SELECT
Specifies the number of data bits in each transmitted or received character.
00 – 5-bit character
01 – 6-bit character
10 – 7-bit character
11 – 8-bit character
Table 17-14. LCR Bit Definitions (Sheet 2 of 2)
Physical Address
0x4160_000C
Line Control Register (LCR) PXA255 Processor Hardware UART
Bit 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
reserved
DL
A
B
SB
ST
K
Y
P
EPS PEN STB WL
S
Reset ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? 0 0 0 0 0 0 0 0
Bits Name Description