XR16C2850CM48 EXAR [Exar Corporation], XR16C2850CM48 Datasheet - Page 29

• Manufacturer Part Number: XR16C2850CM48
• Description: 3.3V AND 5V DUART WITH 128-BYTE FIFO
• Manufacturer: EXAR [Exar Corporation]

XR16C2850
REV. 2.0.0
EFR[4]: Enhanced Function Bits Enable
Enhanced function control bit. This bit enables IER
bits 4-7, ISR bits 4-5, FCR bits 4-5, and MCR bits 5-7
to be modified. After modifying any enhanced bits,
EFR bit-4 can be set to a logic 0 to latch the new val-
ues. This feature prevents legacy software from alter-
ing or overwriting the enhanced functions once set.
Normally, it is recommended to leave it enabled, logic
1.
• Logic 0 = modification disable/latch enhanced fea-
• Logic 1 = Enables the above-mentioned register
EFR[5]: Special Character Detect Enable
• Logic 0 = Special Character Detect Disabled
• Logic 1 = Special Character Detect Enabled. The
tures. IER bits 4-7, ISR bits 4-5, FCR bits 4-5, and
MCR bits 5-7 are saved to retain the user settings.
After a reset, the IER bits 4-7, ISR bits 4-5, FCR
bits 4-5, and MCR bits 5-7are set to a logic 0 to be
compatible with ST16C550 mode (default).
bits to be modified by the user.
(default).
UART compares each incoming receive character
with data in Xoff-2 register. If a match exists, the
receive data will be transferred to FIFO and ISR bit-
4 will be set to indicate detection of the special
EFR
C
ONT
X
X
X
0
0
1
0
1
1
0
1
0
BIT
-3
-3
EFR
C
ONT
X
X
X
0
0
0
1
1
0
1
1
0
BIT
-2
-2
3.3V AND 5V DUART WITH 128-BYTE FIFO
T
ABLE
EFR
C
ONT
15: S
X
X
X
X
0
0
1
0
1
1
1
1
BIT
-1
-1
OFTWARE
EFR
C
ONT
0
X
X
X
X
0
0
1
1
1
1
1
F
BIT
29
LOW
-0
-0
EFR[6]: Auto RTS Flow Control Enable
RTS# output may be used for hardware flow control
by setting EFR bit-6 to logic 1. When Auto RTS is se-
lected, an interrupt will be generated when the re-
ceive FIFO is filled to the programmed trigger level
and RTS de-asserts to a logic 1 at the next upper trig-
ger level or hysteresis level. RTS# will return to a logic
0 when FIFO data falls below the next lower trigger
level. The RTS# output must be asserted (logic 0) be-
fore the auto RTS can take effect. RTS# pin will func-
tion as a general purpose output when hardware flow
control is disabled.
• Logic 0 = Automatic RTS flow control is disabled
• Logic 1 = Enable Automatic RTS flow control.
C
character. Bit-0 corresponds with the LSB bit of the
receive character. If flow control is set for compar-
ing 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, if
enabled via IER bit-5.
(default).
ONTROL
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
T
RANSMIT AND
F
UNCTIONS
R
ECEIVE
S
OFTWARE
F
LOW
C
ONTROL