xr16c864iq Exar Corporation, xr16c864iq Datasheet - Page 27

• Manufacturer Part Number: xr16c864iq
• Description: Quad Uart With Rx/tx Fifo Counters And 128-byte Fifo
• Manufacturer: Exar Corporation

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REV. 2.0.1
]
ISR[0]: Interrupt Status
ISR[3:1]: Interrupt Status
These bits indicate the source for a pending interrupt at interrupt priority levels (See Interrupt Source Table 10).
ISR[5:4]: Interrupt Status
These bits are enabled when EFR bit-4 is set to a logic 1. ISR bit-4 indicates that the receiver detected a data
match of the Xoff character(s). Note that once set to a logic 1, the ISR bit-4 will stay a logic 1 until a Xon
character is received. ISR bit-5 indicates that CTS# or RTS# has changed state.
ISR[7:6]: FIFO Enable Status
These bits are set to a logic 0 when the FIFOs are disabled. They are set to a logic 1 when the FIFOs are
enabled.
This register is used to enable the FIFOs, clear the FIFOs, set the transmit/receive FIFO trigger levels, and
select the DMA mode. The DMA and FIFO modes are defined as follows:
FCR[0]: TX and RX FIFO Enable
FCR[1]: RX FIFO Reset
This bit is only active when FCR bit-0 is a ‘1’.
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4.5
P
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).
Logic 0 = Disable the transmit and receive FIFO (default).
Logic 1 = Enable the transmit and receive FIFOs. This bit must be set to logic 1 when other FCR bits are
written or they will not be programmed.
Logic 0 = No receive FIFO reset (default)
Logic 1 = Reset the receive FIFO pointers and FIFO level counter logic (the receive shift register is not
cleared or altered). This bit will return to a logic 0 after resetting the FIFO.
RIORITY
L
EVEL
1
2
3
4
5
6
7
-
FIFO Control Register (FCR) - Write-Only
B
IT
0
0
0
0
0
0
1
0
-5
B
IT
0
0
0
0
0
1
0
0
-4
ISR R
B
EGISTER
T
IT
0
1
0
0
0
0
0
0
ABLE
-3
10: I
B
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
27
B
2.97V TO 5.5V QUAD UART WITH 128-BYTE FIFO
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
XR16C864