XR20M1172G28-0B Datasheet, PDF (30/55 Pages) Exar Corporation – TWO CHANNEL I2C/SPI UART WITH 64-BYTE FIFO

XR20M1172
TWO CHANNEL I2C/SPI UART WITH 64-BYTE FIFO
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TABLE 9: INTERRUPT SOURCE AND PRIORITY LEVEL
REV. 1.2.0
PRIORITY
ISR REGISTER STATUS BITS
SOURCE OF INTERRUPT
LEVEL BIT-5 BIT-4 BIT-3 BIT-2 BIT-1
BIT-0
1
0
0
0
1
1
0 LSR (Receiver Line Status Register)
2
0
0
1
1
0
0 RXRDY (Receive Data Time-out)
3
0
0
0
1
0
0 RXRDY (Received Data Ready)
4
0
0
0
0
1
0 TXRDY (Transmit Ready)
5
0
0
0
0
0
0 MSR (Modem Status Register)
6
1
1
0
0
0
0 GPIO (General Purpose Inputs)
7
0
1
0
0
0
0 RXRDY (Received Xoff or Special character)
8
1
0
0
0
0
0 CTS#, RTS# change of state
-
0
0
0
0
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 Table 9).
ISR[4]: Xoff/Xon or Special Character Interrupt Status
This bit is set when EFR[4] = 1 and IER[5] = 1. ISR bit-4 indicates that the receiver detected a data match of
the Xoff character(s). If this is an Xoff interrupt, it is cleared when XON is received. If it is a special character
interrupt, it is cleared by reading ISR.
ISR[5]: RTS#/CTS# Interrupt Status
This bit is enabled when EFR[4] = 1. ISR bit-5 indicates that the CTS# or RTS# has been de-asserted.
ISR[7:6]: FIFO Enable Status
In Non-FIFO Mode, these bits are a logic 0. In FIFO Mode, these bits are a logic 1.
4.5 FIFO Control Register (FCR) - Write-Only
This register is used to enable the FIFOs, clear the FIFOs and set the transmit/receive FIFO trigger levels.
FCR[0]: TX and RX FIFO Enable
• Logic 0 = Non-FIFO Mode (default). Transmit and receive FIFOs disabled for 16450 compatibility. For
normal operation, the FIFO Mode must be enabled.
• Logic 1 = FIFO Mode. Enable the transmit and receive FIFOs. This bit must be set to a logic 1 when other
FCR bits are written or they will not be programmed.
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