XR88C681_06 Datasheet, PDF (79/101 Pages) Exar Corporation – CMOS Dual Channel UART (DUART)

XR88C681
H. SPECIAL MODES OF OPERATION
H.1.1 Receiver-Controlled RTS/CTS Handshaking
H.1 RTS/CTS Handshaking
The DUART can be programmed to support RTS/CTS
Handshaking, as a means of data flow control with other
devices. This section will describe a couple of options that
the DUART allows the user in implementing RTS/CTS
Handshaking. Specifically, these options are:
D Receiver-Controlled RTS/CTS Handshaking
D Transmitter-Controlled RTS/CTS Handshaking
In this mode, the Receiver has the ability to automatically
negate the RTS output (to the Transmitting device).
Specifically, this mode allows the Receiver to negate the
RTS signal if its RHR is full; and, is thereby, very effective
in preventing Receiver Overrun Errors. Figure 42
presents a diagram of an example illustrating the
operation of the Receiver-Controlled RTS configuration.
Receiving Device
RTSA
(OP0)
RXDA
TXDA
FFULLA
CTSA
(IP0)
(OP4)
To CPU
FFULLA
RTSA
RXDA
Transmitting Device
CTSB
(IP1)
TXDB
RXDB
RTSB
(OP1)
Figure 42. Block Diagram and Timing Sequence of Two DUARTs Connected
in the Receiver-RTS Controlled Configuration
Rev. 2.11
79