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ST16C1450/51
2.97V TO 5.5V UART
á
REV. 4.2.0
16
4.4.1
LSR is by any of the LSR bits 1, 2, 3 and 4.
RXRDY is by received data in RHR.
TXRDY is by THR empty.
MSR is by any of the MSR bits 0, 1, 2 and 3.
4.4.2
Interrupt Clearing:
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 RHR).
RXRDY interrupt is cleared by reading RHR.
TXRDY interrupt is cleared by a read to the ISR register AND disabling the TXRDY interrupt (set IER bit-1 =
0), or by loading data into the TX FIFO.
MSR interrupt is cleared by a read to the MSR register.
Interrupt Generation:
]
ISR[0]: Interrupt Status
Logic 0 = An interrupt is pending and the ISR contents may be used as a pointer to the appropriate interrupt
service routine.
Logic 1 = No interrupt pending (default condition).
ISR[3:1]: Interrupt Status
These bits indicate the source for a pending interrupt at interrupt priority levels (See Interrupt Source
Table 4
).
ISR[7:4]: Reserved
4.5
The Line Control Register is used to specify the asynchronous data communication format. The word or
character length, the number of stop bits, and the parity are selected by writing the appropriate bits in this
register.
Line Control Register (LCR) - Read/Write
T
ABLE
4: I
NTERRUPT
S
OURCE
AND
P
RIORITY
L
EVEL
P
RIORITY
L
EVEL
ISR R
EGISTER
S
TATUS
B
ITS
S
OURCE
OF
INTERRUPT
B
IT
-3
B
IT
-2
B
IT
-1
B
IT
-0
1
0
1
1
0
LSR (Receiver Line Status Register)
2
0
1
0
0
RXRDY (Received Data Ready)
3
0
0
1
0
TXRDY (Transmit Ready)
4
0
0
0
0
MSR (Modem Status Register)
-
0
0
0
1
None (default)