4/29/2020
Godson 3A1000 Processor User Manual
95
Bit field
Bit field name
Bit width access
description
7: 4
Reserved
4
RW
Keep
3
IME
1
RW
Modem status interrupt enable '0' – close '1' – open
2
ILE
1
RW
Receiver line status interrupt enable '0' – close '1' – open
1
ITxE
1
RW
The transfer save register is empty and interrupt enable '0'-turn off '1'-hit
open
0
IRxE
1
RW
Receive valid data interrupt enable '0' – close '1' – open
10.3.3
Interrupt Identification Register ( IIR )
Chinese name: Interrupt source register
105
Page 118
Godson 3A1000 Processor User Manual Part 1
Register bit width: [7: 0]
Offset: 0x02
Reset value: 0xc1
Bit field
Bit field name
Bit width access
description
7: 4
Reserved
4
R
Keep
3: 1
II
3
R
Interrupt source display bit, see the table below for details
0
INTp
1
R
Interrupt indication bit
Interrupt control function table
Bit 3
Bit 2 Bit 1 Priority
Type of interrupt
Interrupt source
Interrupt reset control
0
1
1
1st
Receiving line
state
Parity, overflow, or frame error, or
Interrupt
Read LSR
0
1
0
2nd
Received valid
data
The number of characters in the FIFO reaches
trigger level
Low number of characters in FIFO
Value for trigger
1
1
0
2nd
Receive timeout There is at least one character in the FIFO,
But not in 4 character time
Any operation, including read and write operations
Make
Read receive FIFO
0
0
1
3rd
Transmit, save, send
The memory is empty
Transfer save register is empty
Write data to THR or
Multi IIR
0
0
0
4th
Modem status CTS, DSR, RI or DCD.
Read MSR
10.3.4
FIFO control register ( FCR )
Chinese name: FIFO control register
Register bit width: [7: 0]
Offset: 0x02
Reset value: 0xc0
Bit field
Bit field name
Bit width access
description
7: 6
TL
2
W
Trigger value '00' of the interrupt request from the receiving FIFO –
1 byte '01' – 4 bytes
'10' – 8 bytes '11' – 14 bytes