XR88C681_06 Datasheet, PDF (84/101 Pages) Exar Corporation – CMOS Dual Channel UART (DUART)

XR88C681
START
ASSERT RTSA
(Write 01h to DUART Address 0Eh)
*CTSA INPUT IS ASSERTED.
Data transmission is now permitted.
Is
TXEMT
Asserted
?
No
Yes
*RTSA is Automatically Negated by
Receiver Controlled RTS Function.
(OP0 toggles “High”)
-CTSA INPUT IS NEGATED.
Data transmission is disabled.
Is
TXRDY
Yes
Negated?
No
Generate “Input Port Change of State”
Interrupt (IP2) in Receiving Device
TOGGLE OP3 (CTS_out) PIN
“LOW”
(Write 08h to DUART Address 0Eh) _No
Is
IP2 = 1
?
Yes
TOGGLE OP3 (CTS_out) PIN
“HIGH”
(Write 08h to DUART Address 0Fh)
Figure 45. A Flow Diagram depicting an Algorithm that could be used to Realize the
Transmitter-Controlled RTS/CTS Handshaking Mode
H.2 Multi-drop (8051 9 bit) Mode
Each serial channel of the DUART can be configured to
operate in a wake up mode useful for multi-drop or
multiprocessor applications. This section will first present
the concept of the Multi-Drop Mode. Afterwards, the
function and procedure of operating the DUART in the
Multi-Drop mode is discussed in Section H.2.1.
H.2.1 Concept of Multi-Drop Mode
This mode is compatible with the serial “Nine bit Mode” of
8051 family microcomputers. In this mode of operation a
“master station”, connected to a maximum of 256 slave
station is possible, as depicted in Figure 46.
Rev. 2.11
84