XR16V564/564D
29
REV. 1.0.4
2.25V TO 3.6V QUAD UART WITH 32-BYTE FIFO
]
TABLE 11: INTERRUPT SOURCE AND PRIORITY LEVEL
PRIORITY
ISR REGISTER STATUS BITS
SOURCE OF INTERRUPT
LEVEL
BIT-5
BIT-4
BIT-3
BIT-2
BIT-1
BIT-0
1
0
1
0
LSR (Receiver Line Status Register)
2
0
1
0
RXRDY (Receive Data Time-out)
3
0
1
0
RXRDY (Received Data Ready)
4
0
1
0
TXRDY (Transmit Ready)
5
0
MSR (Modem Status Register)
6
0
1
0
RXRDY (Received Xoff or Special character)
7
1
0
CTS#, RTS# change of state
-
0
1
None (default)
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
ISR[4]: Interrupt Status (requires EFR bit-4 = 1)
This bit is 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) or a special character.
ISR[5]: Interrupt Status (requires EFR bit-4 = 1)
ISR bit-5 indicates that CTS# or RTS# has changed state from LOW to HIGH.
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.
4.5
FIFO Control Register (FCR) - Write-Only
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
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.