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Communication Processor Module
MOTOROLA
MPC823 USER’S MANUAL
16-157
SCC2
COMMUNICATION
16
PROCESSOR
MODULE
For synchronous communication, the internal clock is identical to the baud rate output. To
get the preferred rate, you can select the appropriate system clock according to the following
equation:
sync baud rate =
(BRGCLK, CLK1, CLK2, CLK3 or CLK4)
÷ (clock divider + 1) ÷
(1 or 16 according to the DIV16 bit)
To get a rate of 64kbps, the system clock can be 24.96MHz, DIV16 = 0, and the clock
divider = 389.
16.9 THE SERIAL COMMUNICATION CONTROLLER
The MPC823 has a serial communication controller (SCC2) that can be configured
independently to implement different protocols. It can be used to implement bridging
functions, routers, gateways, and interface with a wide variety of standard WANs, LANs, and
proprietary networks. The serial communication controller has many physical interface
options such as interfacing to TDM buses, ISDN buses, and standard modem interfaces.
The serial communication controller does not include the physical interface, but it is the logic
that formats and manipulates the data obtained from the physical interface. That is why the
serial interface is described in a different section. The protocol you choose is independent
of your physical interface preference. The serial communication controller is described in
terms of the protocol that you choose to run. When a serial communication controller is
programmed to implement a certain protocol or mode, a certain level of functionality is
associated with that protocol. For most protocols, this corresponds to the different parts of
the link layer. Many functions of the serial communication controller are common to all of the
following protocols:
UART controller
HDLC controller
HDLC bus controller
AppleTalk/LocalTalk controller
Asynchronous HDLC controller
IrDA controller
Transparent controller
Ethernet controller
Although the selected protocol usually applies to both the SCC2 transmitter and receiver,
the serial communication controller can run half of the serial communication controller with
transparent operation while the other half runs the standard protocol.