xr16v2751im Exar Corporation, xr16v2751im Datasheet - Page 28

• Manufacturer Part Number: xr16v2751im
• Description: High Performance Duart With 64-byte Fifo And Powersave Feature
• Manufacturer: Exar Corporation

XR16V2751
HIGH PERFORMANCE DUART WITH 64-BYTE FIFO AND POWERSAVE FEATURE
FCR[2]: TX FIFO Reset
This bit is only active when FCR bit-0 is a ‘1’.
•
•
FCR[3]: DMA Mode Select
Controls the behavior of the TXRDY# and RXRDY# pins. See DMA operation section for details.
•
•
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.
T
Table-A
Table-B
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.
T
RIGGER
ABLE
FCTR
B
Table 11
IT
0
0
-5
T
ABLE
FCTR
B
IT
0
1
shows the complete selections. Note that the receiver and the transmitter cannot use
11: T
-4
RANSMIT AND
B
FCR
IT
0
0
1
1
0
0
1
1
-7
B
FCR
IT
0
1
0
1
0
1
0
1
-6
R
ECEIVE
B
FCR
IT
0
0
0
1
1
-5
FIFO T
BIT
FCR
28
0
0
1
0
1
-4
RIGGER
T
RIGGER
Table 11
1 (default)
R
ECEIVE
T
14
16
24
28
ABLE AND
4
8
8
L
EVEL
below shows the selections. EFR bit-4
L
1 (default)
T
EVEL
T
RANSMIT
RIGGER
L
EVEL
16
24
30
8
S
ELECTION
16C550, 16C2550,
16C2552, 16C554,
16C580
16C650A
C
OMPATIBILITY
REV. 1.0.1