xr16v2551im Exar Corporation, xr16v2551im Datasheet - Page 17

• Manufacturer Part Number: xr16v2551im
• Description: High Performance Duart With 16-byte Fifo And Powersave Feature
• Manufacturer: Exar Corporation

REV. 1.0.2
The V2551 has a new feature that provides flow control trigger hysteresis while maintaining compatibility with
the XR16C850, ST16C650A and ST16C550 family of UARTs. With the Auto RTS function enabled, an interrupt
is generated when the receive FIFO reaches the selected RX trigger level. The RTS# pin will not be forced
HIGH (RTS off) until the receive FIFO reaches one level above the selected RX trigger level in the trigger table
(Table
trigger level in the trigger table
accept data until the receive FIFO gets full. The Auto RTS function is initiated when the RTS# output pin is
asserted LOW (RTS On).
Automatic CTS flow control is used to prevent data overrun to the remote receiver FIFO. The CTS# input is
monitored to suspend/restart the local transmitter. The auto CTS flow control feature is selected to fit specific
application requirement (see
•
If using the Auto CTS interrupt:
•
2.14
2.15
Enable auto CTS flow control using EFR bit-7.
Enable CTS interrupt through IER bit-7 (after setting EFR bit-4). The UART issues an interrupt when the
CTS# pin is de-asserted (HIGH): ISR bit-5 will be set to 1, and UART will suspend transmission as soon as
the stop bit of the character in process is shifted out. Transmission is resumed after the CTS# input is re-
asserted (LOW), indicating more data may be sent.
R
X
12). The RTS# pin will return LOW after the RX FIFO is unloaded to one level below the selected RX
T
Auto RTS Hysteresis
Auto CTS Flow Control
RIGGER
14
1
4
8
L
EVEL
HIGH PERFORMANCE DUART WITH 16-BYTE FIFO AND POWERSAVE FEATURE
Figure
T
ABLE
(Table
INT P
10):
7: A
IN
12). Under the above described conditions, the V2551 will continue to
A
14
1
4
8
UTO
CTIVATION
RTS (H
ARDWARE
17
RTS# D
(C
HARACTERS IN
) F
E
-
LOW
ASSERTED
14
14
4
8
C
ONTROL
R
X
(H
F
IFO
IGH
)
)
(C
RTS# A
HARACTERS IN
SSERTED
XR16V2551
0
1
4
8
R
(L
X
F
OW
IFO
)
)