XR88C681CP/40 Exar Corporation, XR88C681CP/40 Datasheet - Page 85

• Manufacturer Part Number: XR88C681CP/40
• Description: Dual Channel UART
• Manufacturer: Exar Corporation

Specifications of XR88C681CP/40

• Features: *
• Number Of Channels: 2, DUART
• Fifo's: 1 Byte, 3 Byte
• Voltage - Supply: 5V
• With Parallel Port: Yes
• With Cmos: Yes
• Mounting Type: Through Hole
• Package / Case: 40-DIP (0.600", 15.24mm)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

The “Master Station” communicates to the “Slave
Stations” by transmitting a character (typically a byte) with
an “Address/Data” bit flag appended to the end of the
character. This typically results in nine bits of being
transmitted for every character byte, as presented in
Figure 47.
Rev. 2.11
Figure 47. Bit Format of Character Data Being Transmitted in the Multi-Drop Mode
Figure 46. An Illustration Depicting the Concept of Multi-Drop Mode
RXDn
00h
LSB
RXDn
8 Bit Character
01h
Master Device
TXDn
Slave Devices
85
When the “Master Station” wants to transmit a block of
data to one of several slaves, it first sends out an Address
byte that identifies the “Target Slave”. An address byte
differs from a data byte in that the ninth bit is a “1” in an
Address Byte and a “0” in a Data Byte.
RXDn
02h
MSB
A/D
Address/Data Bit
RXDn
FFh
XR88C681