xr20v2172 Exar Corporation, xr20v2172 Datasheet - Page 27

• Manufacturer Part Number: xr20v2172
• Description: Two Channel I2c/spi Uart With 64-byte Fifo And Rs232 Transceiver
• Manufacturer: Exar Corporation

REV. 1.0.0
FCR[1]: RX FIFO Reset
This bit is only active when FCR bit-0 is a ‘1’ and requires at least 3 XTAL clocks to reset.
•
•
FCR[2]: TX FIFO Reset
This bit is only active when FCR bit-0 is a ‘1’ and requires at least 3 XTAL clocks to reset.
•
•
FCR[3]: DMA Mode Select
This is a legacy register bit that does not have any functionality in the XR20V2172.
FCR[5:4]: Transmit FIFO Trigger Select (requires EFR bit-4=1)
(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 spaces in the FIFO is above 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.
transmit interrupt when the number of available spaces in the FIFO is less than the transmit trigger level.
Table 10
FCR[7:6]: Receive FIFO Trigger Select
(logic 0 = default, RX trigger level =1)
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 is greater than the receive trigger level or when a receive data
timeout occurs (see
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.
shows the selections.
“Section 2.9, Receiver” on page
T
ABLE
B
FCR
TWO CHANNEL I2C/SPI UART WITH 64-BYTE FIFO AND RS232 TRANSCEIVER
IT
0
0
1
1
-7
10: T
B
FCR
RANSMIT AND
IT
0
1
0
1
-6
B
FCR
IT
0
0
1
1
-5
R
ECEIVE
BIT
FCR
0
1
0
1
-4
27
Table 10
14).
FIFO T
T
(
RIGGER
CHARACTERS
R
ECEIVE
16
56
60
8
RIGGER
shows the selections. The UART will issue a
L
EVEL
)
L
T
EVEL
RIGGER
T
(
SPACES
RANSMIT
S
16
32
56
8
ELECTION
L
EVEL
)
XR20V2172