XR88C681J-F Datasheet, PDF (73/101 Pages) Exar Corporation – Two Full Duplex, Independent Channels

XR88C681
MR2n[7:6] - Channel Mode Select
Each Channel can operate in one of four modes.
D Setting MR2n[7:6] = 00 configures the channel to op-
erate in the Normal Mode. In this mode, the receiver
and transmitter operate independently. Figure 38
presents a diagram depicting Normal Mode Opera-
tion.
D Setting MR2n[7:6] = 01 places the channel in the Auto-
matic Echo Mode, which automatically re-transmits
the received data. Figure 39 presents a diagram de-
picting Automatic Echo Mode Operation. The follow-
ing conditions apply while in this mode.
Incoming ^RXDn
Serial Data
Receive Shift Register
RXCn TXCn
TXDn
Transmit Shift Register
Outgoing Serial
Data
Receive Holding
Register
Transmit Holding
Register
8
To Data Bus
(To be read by the CPU)
8
From Data Bus.
(Parallel data from the CPU)
Figure 38. A Block Diagram Depicting Normal Mode Operation.
Rev. 2.11
73