XR17V258
46
66MHZ PCI BUS OCTAL UART WITH POWER MANAGEMENT SUPPORT
REV. 1.0.2
5.5.1
Interrupt Generation:
LSR is by any of the LSR bits [4:1]. See IER bit [2] description on the previous page.
RXRDY is by RX trigger level.
RXRDY Time-out is by a 4-char plus 12 bits delay timer.
TXRDY is by TX trigger level or TX FIFO empty (or transmitter empty in auto RS-485 control).
MSR is by any of the MSR bits [3:0].
Receive Xon/Xoff/Special character is by detection of a Xon, Xoff or Special character.
CTS#/DSR# is when its transmitter toggles the input pin (from LOW to HIGH) during auto CTS/DSR flow
control enabled by EFR bit [7] and selection on MCR bit [2].
RTS#/DTR# is when its receiver toggles the output pin (from LOW to HIGH) during auto RTS/DTR flow
control enabled by EFR bit [6] and selection on MCR bit [2].
Wake-up indicator is when the UART wakes up from the sleep mode.
5.5.2
Interrupt Clearing:
LSR interrupt is cleared by a read to the LSR register.
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.
Xon or Xoff interrupt is cleared by a read to ISR register.
Special character interrupt is cleared by a read to ISR or after the next character is received.
RTS#/DTR# and CTS#/DSR# status change interrupts are cleared by a read to the MSR register.
Wake-up indicator is cleared by a read to the INT0 register.
]
TABLE 16: INTERRUPT SOURCE AND PRIORITY LEVEL
PRIORITY
ISR REGISTER STATUS BITS
SOURCE OF THE 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 (Received Data Ready)
3
0
1
0
RXRDY (Receive Data Time-out)
4
0
1
0
TXRDY (Transmitter Holding Register Empty)
5
0
MSR (Modem Status Register)
6
0
1
0
RXRDY (Received Xon/Xoff or Special character)
7
1
0
CTS#/DSR#, RTS#/DTR# change of state
X
0
1
None (default)
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.
ISR[5:1]: Interrupt Status
These bits indicate the source for a pending interrupt at interrupt priority levels (See Table 16). See “Section