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Baud Rate Generators (BRGs)
MC68360 USER’S MANUAL
The SCC4 in NMSI mode has its own set of modem control pins:
TXD4
RXD4
TCLK4 <- BRG1–BRG4, CLK5–CLK8
RCLK4 <- BRG1–BRG4, CLK5–CLK8
RTS4
CTS4
CD4
The SMC1 in NMSI mode has its own set of modem control pins:
SMTXD1
SMRXD1
SMCLK1 <- BRG1–BRG4, CLK1–CLK4
SMSYN1 (used only in the totally transparent protocol)
The SMC2 in NMSI mode has its own set of modem control pins:
SMTXD2
SMRXD2
SMCLK2 <- BRG1–BRG4, CLK5–CLK8
SMSYN2 (used only in the totally transparent protocol)
Any SCC or SMC that requires fewer pins that those listed may use that pin for another func-
tion or configure that pin as a parallel I/O pin.
Since some SCCs use external clock pins CLK1–CLK4 and other SCCs use external clock
pins CLK5–CLK8, it might seem that there is no way to provide one external clock source
on one CLK pin to be used by all four SCCs. However, the QUICC provides a simple clock
bridge function from external CLK8 to the internal CLK4 connection, even if the CLK4 pin is
used for another of its programmable functions. This configuration allows SCC1/SCC2 to
share clocks with SCC3/SCC4 without wasting an external pin. This is shown in the port A
registers in 7.14.4 Port A Registers.
7.9 BAUD RATE GENERATORS (BRGS)
The CPM contains four, independent, identical BRGs that can be used with the SCCs and
SMCs. The clocks produced in the BRG are sent to the bank-of-clocks selection logic, where
they can be routed to the SCCs and/or SMCs. The bank-of-clocks logic is described in 7.8.9
NMSI Configuration. In addition, the output of the BRG may be routed to a pin to be used
externally. The main features of the BRGs are as follows:
Four, Independent, Identical BRGs
On-the-Fly Changes Allowed
Each BRG May Be Routed to One or More SCCs or SMCs
A 16
× Divider Option Allows Slow Baud Rates at High System Frequencies
Each BRG Contains an Autobaud Support Option
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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