W83977AF Information Storage Devices, Inc, W83977AF Datasheet - Page 60

• Manufacturer Part Number: W83977AF
• Description: W83877TF Plus Kbc, Cir, RTC
• Manufacturer: Information Storage Devices, Inc

Bit 7, 6: These two bits are set to a logical 1 when UFR bit 0 = 1.
Bit 5, 4: These two bits are always logic 0.
Bit 3: In 16450 mode, this bit is 0. In 16550 mode, both bit 3 and 2 are set to a logical 1 when a time-
Bit 2, 1: These two bits identify the priority level of the pending interrupt, as shown in the table below.
Bit 0: This bit is a logical 1 if there is no interrupt pending. If one of the interrupt sources has
TABLE 3-4 INTERRUPT CONTROL FUNCTION
** Bit 3 of ISR is enabled when bit 0 of UFR is logical 1.
3.2.7
This 8-bit register allows the five types of controller interrupts to activate the interrupt output
signal separately. The interrupt system can be totally disabled by resetting bits 0 through 3 of the
Bit
3
0
0
0
1
0
0
out interrupt is pending.
occurred, this bit will be set to a logical 0.
Bit
2
0
1
1
1
0
0
ISR
Interrupt Control Register (ICR) (Read/Write)
Bit
1
0
1
0
0
1
0
Bit
0
1
0
0
0
0
0
7
Interrupt
priority
First
Second
Second
Third
Fourth
-
6
Interrupt Type
UART Receive
Status
RBR Data Ready
FIFO Data Timeout
TBR Empty
Handshake status
0
5
4
0
-
3
INTERRUPT SET AND FUNCTION
2
Interrupt Source
No Interrupt pending
1. OER = 1
3. NSER = 1 4. SBD = 1
1. RBR data ready
2. FIFO interrupt active level
Data present in RX FIFO for 4
characters period of time since last
access of RX FIFO.
TBR empty
1. TCTS = 1
3. FERI = 1
reached
1
0
W83977F/ W83977AF
2. PBER =1
4. TDCD = 1
2. TDSR = 1
0 if interrupt pending
Interrupt Status bit 0
Interrupt Status bit 1
Interrupt Status bit 2
FIFOs enabled
FIFOs enabled
Publication Release Date: January 1997
PRELIMINARY
Clear Interrupt
Read USR
1. Read RBR
2. Read RBR until FIFO
data under active level
Read RBR
1. Write data into TBR
2. Read ISR (if priority is
Read HSR
- 49 -
third)
Revision 0.50
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