xr16v794iv Exar Corporation, xr16v794iv Datasheet - Page 40

• Manufacturer Part Number: xr16v794iv
• Description: High Performance 2.25v To 3.6v Quad Uart With Fractional
• Manufacturer: Exar Corporation

XR16V794
HIGH PERFORMANCE 2.25V TO 3.6V QUAD UART WITH FRACTIONAL BAUD RATE
EFR[5]: Special Character Detect Enable
•
•
EFR[4]: Enhanced Function Bits Enable
Enhanced function control bit. This bit enables the enhanced functions in IER bits 7:5, ISR bits 5:4, FCR bits
5:4, MCR bits 7:5, 3:2 and MSR 7:2 bits to be modified. After modifying any enhanced bits, EFR bit-4 can be
set to a logic 0 to latch the new values. This feature prevents legacy software from altering or overwriting the
enhanced functions once set. Normally, it is recommended to leave it enabled, logic 1.
•
•
EFR[3:0]: Software Flow Control Select
Combinations of software flow control can be selected by programming these bits, as shown in
below.
Logic 0 = Special Character Detect Disabled (default).
Logic 1 = Special Character Detect Enabled. The UART compares each incoming receive character with
data in Xoff-2 register. If a match exists, the received data will be transferred to FIFO and ISR bit-4 will be set
to indicate detection of the special character. Bit-0 corresponds with the LSB bit for the receive character. If
flow control is set for comparing Xon1, Xoff1 (EFR [1:0]=10) then flow control and special character work
normally. However, if flow control is set for comparing Xon2, Xoff2 (EFR[1:0]=01) then flow control works
normally, but Xoff2 will not go to the FIFO, and will generate an Xoff interrupt and a special character
interrupt.
Logic 0 = modification disable/latch enhanced features. IER bits 7:5, ISR bits 5:4, FCR bits 5:4, MCR bits 7:5,
3:2 and MSR 7:2 bits are saved to retain the user settings. After a reset, all these bits are set to a logic 0 to
be compatible with ST16C550 mode (default).
Logic 1 = Enables the enhanced functions. When this bit is set to a logic 1 all enhanced features are
enabled.
EFR
X
X
X
0
0
1
0
1
1
0
1
0
BIT
-3
EFR
X
X
X
0
0
0
1
1
0
1
1
0
BIT
-2
T
ABLE
EFR
18: S
X
X
X
X
0
0
1
0
1
1
1
1
BIT
-1
OFTWARE
EFR
X
X
X
X
0
0
0
1
1
1
1
1
F
BIT
LOW
40
-0
C
No TX and RX flow control (default and reset)
No transmit flow control
Transmit Xon1, Xoff1
Transmit Xon2, Xoff2
Transmit Xon1 and Xon2, Xoff1 and Xoff2
No receive flow control
Receiver compares Xon1, Xoff1
Receiver compares Xon2, Xoff2
Transmit Xon1, Xoff1
Receiver compares Xon1 or Xon2, Xoff1 or Xoff2
Transmit Xon2, Xoff2
Receiver compares Xon1 or Xon2, Xoff1 or Xoff2
Transmit Xon1 and Xon2, Xoff1 and Xoff2
Receiver compares Xon1 and Xon2, Xoff1 and Xoff2
No transmit flow control
Receiver compares Xon1 and Xon2, Xoff1 and Xoff2
ONTROL
T
RANSMIT AND
F
UNCTIONS
R
ECEIVE
S
OFTWARE
F
LOW
C
REV. 1.0.0
ONTROL
Table 18