xr16l2550im Exar Corporation, xr16l2550im Datasheet - Page 24

• Manufacturer Part Number: xr16l2550im
• Description: Industry Smallest Package Uart With 2.25v To 5.5v Operation
• Manufacturer: Exar Corporation

XR16L2550
LOW VOLTAGE DUART WITH 16-BYTE FIFO
Source Table,
associated with each of these interrupt levels.
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4.4.1
4.4.2
P
LSR is by any of the LSR bits 1, 2, 3 and 4.
RXRDY is by RX trigger level.
RXRDY Time-out is by a 4-char plus 12 bits delay timer.
TXRDY is by TX FIFO empty.
MSR is by any of the MSR bits 0, 1, 2 and 3.
Receive Xoff/Special character is by detection of a Xoff or Special character.
CTS# is when its transmitter toggles the input pin (from low to high) during auto CTS flow control enabled by
EFR bit-7.
RTS# is when its receiver toggles the output pin (from low to high) during auto RTS flow control enabled by
EFR bit-6.
LSR interrupt is cleared by a read to the LSR register (but flags and tags not cleared until character(s) that
generated the interrupt(s) has been emptied or cleared from FIFO).
RXRDY interrupt is cleared by reading data until FIFO falls below the trigger level.
RXRDY Time-out interrupt is cleared by reading RHR.
TXRDY interrupt is cleared by a read to the ISR register or writing to THR.
MSR interrupt is cleared by a read to the MSR register.
Xoff interrupt is cleared by a read to ISR or when Xon character(s) is received.
Special character interrupt is cleared by a read to ISR or after the next character is received.
RTS# and CTS# flow control interrupts are cleared by a read to the MSR register.
RIORITY
L
EVEL
1
2
3
4
5
6
7
-
Interrupt Generation:
Interrupt Clearing:
B
IT
0
0
0
0
0
0
1
0
Table
-5
B
9, shows the data values (bit 0-5) for the interrupt priority levels and the interrupt sources
IT
0
0
0
0
0
1
0
0
-4
ISR R
B
EGISTER
IT
T
0
1
0
0
0
0
0
0
ABLE
-3
B
9: I
S
IT
TATUS
1
1
1
0
0
0
0
0
-2
NTERRUPT
B
B
ITS
IT
1
0
0
1
0
0
0
0
-1
S
OURCE AND
24
B
IT
0
0
0
0
0
0
0
1
-0
LSR (Receiver Line Status Register)
RXRDY (Receive Data Time-out)
RXRDY (Received Data Ready)
TXRDY (Transmit Ready)
MSR (Modem Status Register)
RXRDY (Received Xoff or Special character)
CTS#, RTS# change of state
None (default)
P
RIORITY
L
EVEL
S
OURCE OF INTERRUPT
REV. 1.1.2