Allwinner A20 - Page 614

A20 User Manual (Revision 1.2) Copyright © 2013 Allwinner Technology Co., Ltd. All Rights Reserved. Page 614 / 812
Interrupt
ID
Priority
Level
Interrupt
Type
Interrupt Source
Interrupt Reset
0001
-
None
None
-
0110
Highest
Receiver
line
status
Overrun/parity/ framing
errors or break interrupt
Reading the line status register
0100
Second
Received
data
available
Receiver data available
(non-FIFO mode or FIFOs
disabled) or RCVR FIFO
trigger level reached
(FIFO mode and FIFOs
enabled)
Reading the receiver buffer
register (non-FIFO mode or
FIFOs disabled) or the FIFO
drops below the trigger level
(FIFO mode and FIFOs
enabled)
1100
Second
Characte
r timeout
indication
No characters in or out of
the RCVR FIFO during
the last 4 character times
and there is at least
1character in it during
This time
Reading the receiver buffer
register
0010
Third
Transmit
holding
register
empty
Transmitter holding
register empty (Program
THRE Mode disabled) or
XMIT FIFO at or below
threshold (Program THRE
Mode enabled)
Reading the IIR register (if
source of interrupt); or, writing
into THR (FIFOs or THRE Mode
not selected or disabled) or
XMIT FIFO above threshold
(FIFOs and THRE Mode
selected and enabled).
0000
Fourth
Modem
status
Clear to send or data set
ready or ring indicator or
data carrier detect. Note
that if auto flow control
mode is enabled, a
change in CTS (that is,
DCTS set) does not
cause an interrupt.
Reading the Modem status
Register
0111
Fifth
Busy
detect
indication
UART_16550_COMPATI
BLE = NO and master
has tried to write to the
Line Control Register
while the UART is busy
(USR[0] is set to one).
Reading the UART status
register