mpc823rg Freescale Semiconductor, Inc, mpc823rg Datasheet - Page 657

• Manufacturer Part Number: mpc823rg
• Description: Mpc823 Powerquicc Integrated Communications Processor For Portable Systems
• Manufacturer: Freescale Semiconductor, Inc

16.9.15.7 RECOGNIZING ADDRESSES IN SCCx UART MODE. In multidrop systems,
more than two stations can be present on a network and each one can have a specific
address. Figure 16-73 illustrates two examples of this configuration. Frames that consist of
many characters can be broadcast as long as the first character is the destination address.
To achieve this, the UART frame is extended by one bit to distinguish between an address
character and the data characters. The SCCx UART controller can be configured to operate
in a multidrop environment that supports the following two modes:
The SCCx UART controller has two 16-bit address registers that support address
recognition—UADDR1 and UADDR2. The upper 8 bits of these registers must be written
with zero because only the lower 8 bits are used. In automatic mode, the incoming address
is checked against UADDR1 and UADDR2 and when a match is made, the AM bit in the
buffer descriptor is set to indicate the matched address character and the data following it
is written to the data buffers.
• CLOSE RX BD—This command forces a serial communication controller to close the
• INIT RX PARAMETERS —This command initializes all receive parameters in this serial
• Automatic Multidrop Mode—The SCCx UART controller automatically checks the
• Manual Multidrop Mode—The SCCx UART controller receives all characters. An
RX buffer descriptor if it is currently being used and it uses the next buffer descriptor for
any subsequently received data. If a serial communication controller is not in the
process of receiving data, no action is taken.
channel’s parameter RAM to their reset state and must only be issued when the
receiver is disabled. Notice that the INIT TX AND RX PARAMS command can be used
to reset the receive and transmit parameters.
incoming address character and accepts the data following it, but only if the address
matches one of two preset values.
address character is always written to a new buffer and it can be followed by data
characters.
Note: The CLOSE RX BD command in the SCCx UART controller functions the same
Note: For characters less than 8 bits, the most-significant bits must be zero.
as the ENTER HUNT MODE command, except for one difference. CLOSE RX
BD does not need an idle character to be present on the line before it continues
receiving.
Freescale Semiconductor, Inc.
For More Information On This Product,
MPC823 REFERENCE MANUAL
Go to: www.freescale.com
Communication Processor Module
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