xr16m2751 Exar Corporation, xr16m2751 Datasheet - Page 28

• Manufacturer Part Number: xr16m2751
• Description: High Performance Duart With 64-byte Fifo And Powersave
• Manufacturer: Exar Corporation

XR16M2751
1.62V TO 3.63V HIGH PERFORMANCE DUART WITH 64-BYTE FIFO
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
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FCR[1]: RX FIFO Reset
This bit is only active when FCR bit-0 is a ‘1’.
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FCR[2]: TX FIFO Reset
This bit is only active when FCR bit-0 is a ‘1’.
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•
FCR[3]: DMA Mode Select
Controls the behavior of the TXRDY# and RXRDY# pins. See DMA operation section for details.
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FCR[5:4]: Transmit FIFO Trigger Select
(logic 0 = default, TX trigger level = 1)
These 2 bits set the trigger level for the transmit FIFO. The UART will issue a transmit interrupt when the
number of characters in the FIFO falls below the selected trigger level, or when it gets empty in case that the
FIFO did not get filled over the trigger level on last re-load.
must be set to ‘1’ before these bits can be accessed. Note that the receiver and the transmitter cannot use
different trigger tables. Whichever selection is made last applies to both the RX and TX side.
FCR[7:6]: Receive FIFO Trigger Select
(logic 0 = default, RX trigger level =1)
The FCTR Bits 5-4 are associated with these 2 bits. These 2 bits are used to set the trigger level for the receive
FIFO. The UART will issue a receive interrupt when the number of the characters in the FIFO crosses the
trigger level.
different trigger tables. Whichever selection is made last applies to both the RX and TX side.
4.5
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.
Logic 0 = No transmit FIFO reset (default).
Logic 1 = Reset the transmit FIFO pointers and FIFO level counter logic (the transmit shift register is not
cleared or altered). This bit will return to a logic 0 after resetting the FIFO.
Logic 0 = Normal Operation (default).
Logic 1 = DMA Mode.
FIFO Control Register (FCR) - Write-Only
Table 11
shows the complete selections. Note that the receiver and the transmitter cannot use
28
Table 11
below shows the selections. EFR bit-4
REV. 1.0.0