CP3BT10 Datasheet, PDF (115/210 Pages) National Semiconductor (TI) – Reprogrammable Connectivity Processor with Bluetooth and USB Interfaces

of the RSFT register are copied into the URBUF register from the URBUF register. The RSFT register is not software
and the Receive Buffer Full bit (URBF) is set. The URBF bit accessible.
is automatically reset when software reads the character
Control and
Error Detection
Parity
Generator/Checker
Transmitter
Baud Clock
System Clock
Flow Control
Logic
Baud Rate
Generator
Baud Clock
Receiver
Figure 41. UART Block Diagram
TXD
RTS
CTS
RXD
DS163
16 1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16 1
Sample
STARTBIT
Sample
DATA (LSB)
16 1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16 1
DATABIT
Sample
DS061
Figure 42. UART Asynchronous Communication
19.2.2 Attention Mode
The Attention mode is available for networking this device
with other processors. This mode requires the 9-bit data for-
mat with no parity. The number of start bits and number of
stop bits are programmable. In this mode, two types of 9-bit
characters are sent on the network: address characters
consisting of 8 address bits and a 1 in the ninth bit position
and data characters consisting of 8 data bits and a 0 in the
ninth bit position.
While in Attention mode, the UART receiver monitors the
communication flow but ignores all characters until an ad-
dress character is received. On receiving an address char-
acter, the contents of the receive shift register are copied to
the receive buffer. The URBF bit is set and an interrupt (if
enabled) is generated. The UATN bit is automatically
cleared, and the UART begins receiving all subsequent
characters. Software must examine the contents of the UR-
BUF register and respond by accepting the subsequent
characters (by leaving the UATN bit reset) or waiting for the
next address character (by setting the UATN bit again).
The operation of the UART transmitter is not affected by the
selection of this mode. The value of the ninth bit to be trans-
mitted is programmed by setting or clearing the UXB9 bit in
115
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