XR16C2850CM48 EXAR [Exar Corporation], XR16C2850CM48 Datasheet - Page 13

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

XR16C2850
REV. 2.0.0
N
on page 23).
Automatic RTS hardware flow control is used to pre-
vent data overrun to the local receiver FIFO. The
RTS# output is used to request remote unit to sus-
pend/resume data transmission. The auto RTS flow
control features is enabled to fit specific application
requirement (see Figure 11):
• Enable auto RTS flow control using EFR bit-6.
• The auto RTS function must be started by asserting
• Enable RTS interrupt through IER bit-6 (after set-
The 2850 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 in-
terrupt is generated when the receive FIFO reaches
the programmed RX trigger level. The RTS# pin will
not be forced to a logic 1 (RTS off), until the receive
FIFO reaches the upper limit of the hysteresis level.
The RTS# pin will return to a logic 0 after the RX
2.12 A
2.13 A
OTE
F
RTS# output pin (MCR bit-1 to logic 1 after it is
enabled).
ting EFR bit-4). The UART issues an interrupt when
the RTS# pin makes a transition from low to high:
ISR bit-5 will be set to logic 1.
IGURE
:
Receive Data
Byte and Errors
Table-B selected as Trigger Table for Figure 10 (Table 10
UTO
128 bytes by 11-bit
UTO
10. R
16X or 8X
wide FIFO
RTS (H
Clock
RTS H
ECEIVER
YSTERESIS
ARDWARE
O
PERATION IN
) F
Receive Data Shift
Register (RSR)
3.3V AND 5V DUART WITH 128-BYTE FIFO
LOW
Data FIFO
Receive
Receive
C
Data
ONTROL
FIFO
AND
Data falls to 8
FIFO Trigger=16
Data fills to 24
Validation
Data Bit
A
UTO
Example:
- RX FIFO trigger level selected at 16 bytes
13
RTS F
FIFO is unloaded to the lower limit of the hysteresis
level.
2850 will continue to accept data until the receive
FIFO gets full. The Auto RTS function is initiated
when the RTS# output pin is asserted to a logic 0
(RTS On). Table 13 shows the complete details for
the Auto RTS# Hysteresis levels. Please note that
this table is for programmable trigger levels only (Ta-
ble D). The hysteresis values for Tables A-C are the
next higher and next lower trigger levels in the corre-
sponding table.
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 Figure 11):
• Enable auto CTS flow control using EFR bit-7.
• - Enable CTS interrupt through IER bit-7 (after set-
2.14 A
ting EFR bit-4). The UART issues an interrupt when
the CTS# pin is de-asserted (logic 1): 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 (logic 0), indicating more
data may be sent.
RTS# re-asserts when data falls below the flow
control trigger level to restart remote transmitter.
Enable by EFR bit-6=1, MCR bit-1.
RTS# de-asserts when data fills above the flow
control trigger level to suspend remote transmitter.
Enable by EFR bit-6=1, MCR bit-1.
(See Note Below)
LOW
RHR Interrupt (ISR bit-2) programmed for
desired FIFO trigger level.
FIFO is Enabled by FCR bit-0=1
Under the above described conditions, the
UTO
C
ONTROL
CTS F
LOW
M
ODE
Receive Data Characters
C
ONTROL
RXFIFO1