XC161 Datasheet, PDF (170/419 Pages) Infineon Technologies AG – 16-Bit Single-Chip Microcontroller with C166SV2 Core Volume 2 (of 2): Peripheral Units

18.5
XC161 Derivatives
Peripheral Units (Vol. 2 of 2)
Asynchronous/Synchronous Serial Interface (ASC)
Autobaud Detection
18.5.1 General Operation
Autobaud Detection provides a capability to recognize the mode and the baudrate of an
asynchronous input signal at RxD. Generally, the baudrates to be recognized must be
known by the application. With this knowledge always a set of nine baudrates can be
detected. The Autobaud Detection is not designed to calculate a baudrate of an unknown
asynchronous frame.
Figure 18-16 shows how the Autobaud Detection is integrated into its Asynchronous
Mode configuration. The RxD data line is an input to the autobaud detection unit. The
clock f_DIV, generated by the fractional divider, is used by the autobaud detection unit as
time base. After successful recognition of baudrate and Asynchronous Mode of the RxD
data input signal, bits in register ASCx_CON and the value of register ASCx_BG in the
baudrate timer are set to the appropriate values, and the ASC can start immediately with
the reception of serial input data.
Asynchronous Mode
f_ASC
Prescaler /
Fractional
f_DIV
Divider
Autobaud
Detection
Baudrate
Timer
Serial Port
Control
RxD
IrDA
Decoding
MUX
Receive / Transmit
Buffers and
Shift Registers
IrDA
Decoding
MUX
TxD
MCA05447
Figure 18-16 Asynchronous Mode Block Diagram
Note: Autobaud detection is not available in Synchronous Mode.
The following sequence must be executed to start the autobaud detection unit:
• Definition of the baudrates to be detected: standard or non-standard baudrates
• Programming of the prescaler/fractional divider to select a specific value of f_DIV
• Starting the prescaler/fractional divider (setting bit R)
• Preparing the interrupt system
• Enabling the autobaud detection (setting bit EN and the interrupt enable bits in
ABCON for interrupt generation, if required)
• Polling interrupt request flag or waiting for the autobaud detection interrupt
User’s Manual
ASC_X, V2.0
18-27
V2.2, 2004-01